I have a BV8000 PRO, it works fine on both AT&T and T-MOBILE network.
So I'm happy to upgrade it to BV9000 PRO, and I just got it today.
When I put my old SIM cards on BV9000 PRO, it can't find service on AT&T network. T-Mobile works fine though.
I don't know how to return it on TOMTOP, but I will try.
I do some search and and found this discussion, seems this is a common problem.
https://forum.xda-developers.com/androi ... r-t3739470
Please find a solution. Please!