Error occuring in aws console when attempting to delete Pinpoint SMS registration and release toll free number.

Please open a case with AWS Support.

As per CLI Documentation https://docs.aws.amazon.com/cli/latest/reference/pinpoint-sms-voice-v2/delete-registration.html

1. Use the delete-registration-attachment AWS CLI command to disassociate any phone numbers, sender IDs, or other resources attached to the registration:

aws pinpoint-sms-voice-v2 delete-registration-attachment --registration-id <registrationId> --resource-arn <resourceArn>

2. Check if the phone number or sender ID is still in use by other registrations and disassociate it from those as well.

3. Once all associated resources are removed, delete the registration itself using the delete-registration command:

aws pinpoint-sms-voice-v2 delete-registration --registration-id <registrationId>

4. Similarly, for toll-free numbers, check if they are associated with any other resources like registrations, pools, etc., and disassociate them before attempting to release the number.