I have an ATT S10e that is unlocked by ATT. I'm currently using with Tmobile and considering upgrading the firmware to Tmobile firmware. I'm curious if I install the TMO firmware, will the phone become locked to TMO and will it need to be unlocked again. The ATT and TMO locking process is different, so my concern is TMO may not be able to unlock even though on TMO firmware because it is not in their database since the phone was an ATT phone. Thanks!