After migration from sprint

Yes I am having the same exact problem because I wanted to use my backup phone he T-Mobile sim card that is in my primary phone will NOT work in my backup phone even though the phone sees it and recognizes it as t mobile but it will NOT work because of some unknown reason SPRINT has LOCKED this sim to the primary phone ONLY even though its a T-Mobile phone and sim card.

  I just got done talking with there TECH support ( 2.5 Hours ) and they have NO idea why its locked but my guess is because my billing is still sprint even though everything else is COMPLETELY T-Mobile.

  My Primary phone and my backup phone are fully unlocked and I also went to T-Mobile store to verify this and they tested my phones with other sim cards and they worked perfectly fine making calls and data connection everything worked .

 They even tried a Brand NEW phone off the shelf and inserted my sim card and the phone saw what the sim was and recognized it as T-Mobile and my # but would NOT allow any calls or Data Connection.

 The tech support told me that on March 31 2022 the migration will be AUTOMATIC on that day and everything will be Migrated then even though the system will NOT allow me to finish Migration of account WITHOUT FORCING me to change plans or prices..

here is a TMO report I found that states I will NOT loose anything and my plan will remain as it is Just will have to reactivate Autopay because that feature will not be migrated over.

Here is the link I found:::https://tmo.report/2022/01/exclusive-t-mobile-wont-make-sprint-customers-change-their-plan/