Moving ACS SMS Number to New Subscription

Question

We are using Azure Communication Services (ACS) for SMS and outbound calling.

Currently, our SMS-enabled phone number is tied to an ACS resource in a prototype subscription that will be decommissioned.

Can you confirm:

1. Is it possible to move or transfer this phone number to another ACS resource or subscription?
2. If not, what is the recommended way to retain the same number in a new subscription (e.g., porting vs. release and reacquire)?
3. Are there any risks or downtime considerations we should be aware of?

We want to ensure a smooth transition before decommissioning the current subscription.

Answer 1

Hii @Anand Singh Bhandari ,

Thank you for reaching us regarding the issue.

1. Is it possible to move or transfer an ACS phone number to another ACS resource or subscription?

No. Azure Communication Services phone numbers are resource‑bound. Microsoft documentation does not support moving or transferring phone numbers between ACS resources or across Azure subscriptions.

Additionally, ACS phone numbers are not supported in Azure Resource Manager (ARM) move operations, meaning they cannot be moved with the ACS resource itself to another subscription.

2. If not, what is the recommended way to retain the same number in a new subscription (e.g., porting vs. release and reacquire)?
   Phone number porting:

• ACS supports port‑in of phone numbers from external carriers into an ACS resource.
• Porting is intended for numbers owned outside of Azure.
• The documentation does not describe a supported process to port a phone number from one ACS resource to another ACS resource, even if both subscriptions belong to the same tenant.

Release and reacquire:

• Releasing and attempting to reacquire the same number carries a risk of permanent number loss and is not guaranteed.

Risks and downtime considerations:
Deleting an ACS resource releases all associated phone numbers, immediately stopping SMS and calling. These numbers can’t be reassigned during the billing cycle and may not be recoverable, risking service downtime and permanent loss.

To ensure a smooth transition:

• Create a new ACS resource in the target subscription
• Provision a new phone number
• Update applications and configurations to use the new number
• Do not delete the existing ACS resource until migration is complete

Reference:
https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/move-support-resources#microsoftcommunication
https://learn.microsoft.com/en-us/azure/communication-services/quickstarts/telephony/port-phone-number
https://learn.microsoft.com/en-us/azure/communication-services/quickstarts/telephony/get-phone-number?tabs=windows&pivots=platform-azp-new

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Answer 2

1. The provided information does not describe any supported way to move or transfer an existing Azure Communication Services (ACS) phone number between ACS resources or subscriptions.
2. The documented behavior is:
   • When a phone number is released, it remains visible in the ACS resource until the end of the billing cycle and cannot be repurchased until that billing cycle ends.
   • When an ACS resource is deleted, all phone numbers associated with that resource are automatically released at the same time.
   Because of this behavior, “release and reacquire” is constrained: after release (whether explicit or via resource deletion), the number cannot be repurchased until the end of the billing cycle, and there is no guarantee in the documentation that the same number can be reacquired. The context does not describe any ACS-specific porting process or a supported pattern to retain the same number when moving to a different subscription.
3. Risks and downtime considerations based on the documented behavior:
   • Once the ACS resource is deleted, associated numbers are released immediately and become unavailable for use with that resource.
   • After release, the number cannot be repurchased until the end of the billing cycle, which implies a potential period where that exact number cannot be used.
   • There is no documented guarantee that the same number can be reacquired after the billing cycle ends, so continuity of that specific number is not assured.

To minimize risk, avoid deleting the existing ACS resource (and thus releasing the number) until a new number and routing strategy are in place in the target subscription. For high-volume or special-number scenarios, the documentation recommends using the high-volume/special order process described at the linked GitHub page for phone number acquisition.

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References:

• Quickstart: Get and manage phone numbers (platform-azp-new)
• Quickstart: Get and manage phone numbers (platform-azcli)
• Quickstart: Get and manage phone numbers (programming-language-csharp)
• Quickstart: Get and manage phone numbers (programming-language-java)
• Quickstart: Get and manage phone numbers (programming-language-javascript)
• Quickstart: Get and manage phone numbers (programming-language-python)
• Choosing the Right Phone Number for Your Business Messaging Needs

Answer 3

Thank you @Golla Venkata Pavani for quick response. This was really helpful!