How do I keep my phone number if I go Google Fi

[AC Question]

I want to terminate Tmobile and start Fi.

 

[hallux]

Fi allows you to transfer the number. The key is to NOT terminate your T-Mobile service until after you have ported your number.

https://support.google.com/fi/answer/6150327?hl=en&ref_topic=4596517

I should add that if you also have Google Voice on the Google account you wish to use for Fi, you need to decide if you want THAT number for Fi or your existing T-Mobile number. If you wish to keep both, you'll need to move the Google Voice number to another account, and you won't be able to forward that Google Voice number to your Fi number as it is essentially a GV number and you can't forward GV to GV.