Additional features, settings, or issues not covered by specific Microsoft Teams categories
I'm working on this at the moment and my initial port request was rejected as well.
After searching and searching, I discovered that, to port a number away from Microsoft Teams, the admin must email Microsoft's PSTN service desk... I found this information under the "Manage Porting PIN" setting in Microsoft Teams Admin Center > Voice > Phone Numbers:
That "Learn More" link doesn't go anywhere helpful, but here's the link on how to contact the PSTN Service Desk: https://docs.microsoft.com/en-us/microsoftteams/manage-phone-numbers-for-your-organization/contact-pstn-service-desk
You'll need to give them your Tenant ID, which can be found using these instructions: https://docs.microsoft.com/en-us/onedrive/find-your-office-365-tenant-id
When I submitted my request, I heard this back immediately:
Hi, thank you for reaching us! Due to the global situation that is currently being experienced, the Number Porting Team is severely backlogged. We are short on resources and working to clear this backlog on a First-In-First-Out (FIFO) basis.
Our current estimated response time is delayed and approximately of 10 to 12 business days that may change due to the increasing demand. We appreciate your patience, comprehension, and be sure that we'll gladly help you with your request.
So, lame... Hopefully it doesn't take two weeks (or more) while I pay for phone service twice and use temporary numbers. Good luck to you!!!