Transfer of liability

I migrated my Sprint account to T-mobile a few days ago. I have two lines on the account - one is my husband’s and one is mine.  When I asked about us changing the account holder from me to my husband, the person who helped us said that we had to call T-mobile to do that on the phone, that they don’t understand why the people in Customer Service keep sending customers into the store to make that kind of change.  He said we should call in and ask to do a “transfer of liability”.   When I talked to T-mobile today, the agent insisted that we had to go to the store to get a credit check run in order to do the rest of the steps over the phone to change ownership.  He said that the only alternative that we could do completely over the phone was for him to send us to Activations to create a new account with my husband as the account holder and port our numbers to that new account, because that department would do a credit check over the phone.  Is there someone here who can tell me plainly the instructions for what I need to do to make my husband the account holder/owner/responsible billing part instead of me?