Hello Khurana,
Welcome to the community!
You would need to request a Transfer of Repsonsibility (TOR) of the second line. As a part of the process, the recipient of the second line would be required to undergo a credit evaluation. You should note that there would be a fee for the transfer (see here). You should also note that since the line is currently financing a device, they would be required to pay the remaining balance for the device as the financing would not transfer (see Payment Program).
I understand that is not how you intended the device financing to remain. Unfortunately, it wouldn't work the way you had hoped. I don't know the details of your situation. However, if you paid the remaining balance for the device on the second line (TOR), the owner of the second account might re-pay you the monthly charges on your device.
You should note that the forums are community-driven and not intended as a venue for customer services. You would first need to contact customer service and notify them of your intent to transfer the responsibility of the second line. The recipient of the second line would then need to contact them to complete the transfer.
Hope this helps 😀
Cheers
