Verizon review: Continuing to bill account even when service was terminated

After switching cellular service from Verizon to Tmobile, Verizon did not stop our services even though the Tmobile rep had already called them to switch the services. We were told all was taken care of. A month later there were several significant amount of dollars automatically taken out of our bank account. After talking to Verizon rep for over an hour to dispute the charges, he was not quite sure what the final charge was for, and stated that we should have personally called Verizon to terminate our contract. We have switched phone services multiple times in the past , and is typically the reps that handle the switching.