diff --git a/apps/bff/src/subscriptions/sim-management.service.ts b/apps/bff/src/subscriptions/sim-management.service.ts
index 8a69ab6c..c562f33b 100644
--- a/apps/bff/src/subscriptions/sim-management.service.ts
+++ b/apps/bff/src/subscriptions/sim-management.service.ts
@@ -640,7 +640,52 @@ export class SimManagementService {
         throw new BadRequestException('networkType must be either "4G" or "5G"');
       }
 
-      await this.freebititService.updateSimFeatures(account, request);
+      const doVoice =
+        typeof request.voiceMailEnabled === 'boolean' ||
+        typeof request.callWaitingEnabled === 'boolean' ||
+        typeof request.internationalRoamingEnabled === 'boolean';
+      const doContract = typeof request.networkType === 'string';
+
+      if (doVoice && doContract) {
+        // First apply voice options immediately (PA05-06)
+        await this.freebititService.updateSimFeatures(account, {
+          voiceMailEnabled: request.voiceMailEnabled,
+          callWaitingEnabled: request.callWaitingEnabled,
+          internationalRoamingEnabled: request.internationalRoamingEnabled,
+        });
+
+        // Then schedule contract line change after 30 minutes (PA05-38)
+        const delayMs = 30 * 60 * 1000;
+        setTimeout(() => {
+          this.freebititService
+            .updateSimFeatures(account, { networkType: request.networkType })
+            .then(() =>
+              this.logger.log('Deferred contract line change executed after 30 minutes', {
+                userId,
+                subscriptionId,
+                account,
+                networkType: request.networkType,
+              })
+            )
+            .catch(err =>
+              this.logger.error('Deferred contract line change failed', {
+                error: getErrorMessage(err),
+                userId,
+                subscriptionId,
+                account,
+              })
+            );
+        }, delayMs);
+
+        this.logger.log('Scheduled contract line change 30 minutes after voice option change', {
+          userId,
+          subscriptionId,
+          account,
+          networkType: request.networkType,
+        });
+      } else {
+        await this.freebititService.updateSimFeatures(account, request);
+      }
 
       this.logger.log(`Updated SIM features for subscription ${subscriptionId}`, {
         userId,
diff --git a/apps/bff/src/vendors/freebit/freebit.service.ts b/apps/bff/src/vendors/freebit/freebit.service.ts
index 323208a7..2819e7e6 100644
--- a/apps/bff/src/vendors/freebit/freebit.service.ts
+++ b/apps/bff/src/vendors/freebit/freebit.service.ts
@@ -182,10 +182,16 @@ export class FreebititService {
 
       const responseData = (await response.json()) as T;
 
-      // Check for API-level errors
-      const rc = String(responseData?.resultCode ?? "");
-      if (rc !== "100") {
-        const errorMessage = String(responseData.status?.message ?? "Unknown error");
+      // Check for API-level errors (some endpoints return resultCode '101' with message 'OK')
+      const rc = String((responseData as any)?.resultCode ?? "");
+      const statusObj: any = (responseData as any)?.status ?? {};
+      const errorMessage = String((statusObj?.message ?? (responseData as any)?.message ?? "Unknown error"));
+      const statusCodeStr = String(statusObj?.statusCode ?? (responseData as any)?.statusCode ?? "");
+      const msgUpper = errorMessage.toUpperCase();
+      const isOkByRc = rc === "100" || rc === "101";
+      const isOkByMessage = msgUpper === "OK" || msgUpper === "SUCCESS";
+      const isOkByStatus = statusCodeStr === "200";
+      if (!(isOkByRc || isOkByMessage || isOkByStatus)) {
 
         // Provide more specific error messages for common cases
         let userFriendlyMessage = `API Error: ${errorMessage}`;
@@ -200,7 +206,7 @@ export class FreebititService {
         this.logger.error("Freebit API error response", {
           endpoint,
           resultCode: rc,
-          statusCode: responseData.status?.statusCode,
+          statusCode: statusCodeStr,
           message: errorMessage,
           userFriendlyMessage,
         });
@@ -208,7 +214,7 @@ export class FreebititService {
         throw new FreebititErrorImpl(
           userFriendlyMessage,
           rc,
-          String(responseData.status?.statusCode ?? ""),
+          statusCodeStr,
           errorMessage
         );
       }
@@ -230,6 +236,42 @@ export class FreebititService {
     }
   }
 
+  // Make authenticated JSON POST request (for endpoints that require JSON body)
+  private async makeAuthenticatedJsonRequest<T>(endpoint: string, body: Record<string, unknown>): Promise<T> {
+    const authKey = await this.getAuthKey();
+    const url = `${this.config.baseUrl}${endpoint}`;
+    const payload = { ...body, authKey };
+    const response = await fetch(url, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(payload),
+    });
+    if (!response.ok) {
+      const text = await response.text().catch(() => null);
+      this.logger.error('Freebit JSON API non-OK', {
+        endpoint,
+        status: response.status,
+        statusText: response.statusText,
+        body: text?.slice(0, 500),
+      });
+      throw new InternalServerErrorException(`HTTP ${response.status}: ${response.statusText}`);
+    }
+    const data = (await response.json()) as T;
+    const rc = String((data as any)?.resultCode ?? '');
+    if (rc !== '100') {
+      const message = (data as any)?.message || (data as any)?.status?.message || 'Unknown error';
+      this.logger.error('Freebit JSON API error response', {
+        endpoint,
+        resultCode: rc,
+        statusCode: (data as any)?.statusCode || (data as any)?.status?.statusCode,
+        message,
+      });
+      throw new FreebititErrorImpl(`API Error: ${message}`, rc, String((data as any)?.statusCode || ''), message);
+    }
+    this.logger.debug('Freebit JSON API Request Success', { endpoint, resultCode: rc });
+    return data;
+  }
+
   /**
    * Get detailed SIM account information
    */
@@ -602,30 +644,48 @@ export class FreebititService {
     }
   ): Promise<void> {
     try {
-      const request: Omit<FreebititAddSpecRequest, "authKey"> = {
-        account,
-        kind: "MVNO",
-      };
+      const doVoice =
+        typeof features.voiceMailEnabled === 'boolean' ||
+        typeof features.callWaitingEnabled === 'boolean' ||
+        typeof features.internationalRoamingEnabled === 'boolean';
+      const doContract = typeof features.networkType === 'string';
 
-      if (typeof features.voiceMailEnabled === "boolean") {
-        request.voiceMail = features.voiceMailEnabled ? ("10" as const) : ("20" as const);
-        request.voicemail = request.voiceMail; // include alternate casing for compatibility
-      }
-      if (typeof features.callWaitingEnabled === "boolean") {
-        request.callWaiting = features.callWaitingEnabled ? ("10" as const) : ("20" as const);
-        request.callwaiting = request.callWaiting;
-      }
-      if (typeof features.internationalRoamingEnabled === "boolean") {
-        request.worldWing = features.internationalRoamingEnabled
-          ? ("10" as const)
-          : ("20" as const);
-        request.worldwing = request.worldWing;
-      }
-      if (features.networkType) {
-        request.contractLine = features.networkType;
+      if (doVoice) {
+        const talkOption: any = {};
+        if (typeof features.voiceMailEnabled === 'boolean') {
+          talkOption.voiceMail = features.voiceMailEnabled ? '10' : '20';
+        }
+        if (typeof features.callWaitingEnabled === 'boolean') {
+          talkOption.callWaiting = features.callWaitingEnabled ? '10' : '20';
+        }
+        if (typeof features.internationalRoamingEnabled === 'boolean') {
+          talkOption.worldWing = features.internationalRoamingEnabled ? '10' : '20';
+        }
+        await this.makeAuthenticatedRequest<import('./interfaces/freebit.types').FreebititVoiceOptionChangeResponse>(
+          '/mvno/talkoption/changeOrder/',
+          {
+            account,
+            userConfirmed: '10',
+            aladinOperated: '10',
+            talkOption,
+          }
+        );
+        this.logger.log('Applied voice option change (PA05-06)', { account, talkOption });
       }
 
-      await this.makeAuthenticatedRequest<FreebititAddSpecResponse>("/master/addSpec/", request);
+      if (doContract && features.networkType) {
+        await this.makeAuthenticatedJsonRequest<import('./interfaces/freebit.types').FreebititContractLineChangeResponse>(
+          '/mvno/contractline/change/',
+          {
+            account,
+            contractLine: features.networkType,
+          }
+        );
+        this.logger.log('Applied contract line change (PA05-38)', {
+          account,
+          contractLine: features.networkType,
+        });
+      }
 
       this.logger.log(`Updated SIM features for account ${account}`, {
         account,
@@ -636,10 +696,7 @@ export class FreebititService {
       });
     } catch (error: unknown) {
       const message = error instanceof Error ? error.message : String(error);
-      this.logger.error(`Failed to update SIM features for account ${account}`, {
-        error: message,
-        account,
-      });
+      this.logger.error(`Failed to update SIM features for account ${account}`, { error: message, account });
       throw error as Error;
     }
   }
diff --git a/apps/bff/src/vendors/freebit/interfaces/freebit.types.ts b/apps/bff/src/vendors/freebit/interfaces/freebit.types.ts
index c95f4543..513cbb35 100644
--- a/apps/bff/src/vendors/freebit/interfaces/freebit.types.ts
+++ b/apps/bff/src/vendors/freebit/interfaces/freebit.types.ts
@@ -187,6 +187,48 @@ export interface FreebititPlanChangeResponse {
   ipv6?: string;
 }
 
+// PA05-06: MVNO Voice Option Change
+export interface FreebititVoiceOptionChangeRequest {
+  authKey: string;
+  account: string;
+  userConfirmed: '10' | '20';
+  aladinOperated: '10' | '20';
+  talkOption: {
+    voiceMail?: '10' | '20';
+    callWaiting?: '10' | '20';
+    worldWing?: '10' | '20';
+    worldCall?: '10' | '20';
+    callTransfer?: '10' | '20';
+    callTransferNoId?: '10' | '20';
+    worldCallCreditLimit?: string;
+    worldWingCreditLimit?: string;
+  };
+}
+
+export interface FreebititVoiceOptionChangeResponse {
+  resultCode: string;
+  status: {
+    message: string;
+    statusCode: string;
+  };
+}
+
+// PA05-38: MVNO Contract Change (4G/5G)
+export interface FreebititContractLineChangeRequest {
+  authKey: string;
+  account: string;
+  contractLine: '4G' | '5G';
+  productNumber?: string;
+  eid?: string;
+}
+
+export interface FreebititContractLineChangeResponse {
+  resultCode: string | number;
+  status?: unknown;
+  statusCode?: string;
+  message?: string;
+}
+
 export interface FreebititCancelPlanRequest {
   authKey: string;
   account: string;