Overcharged During Travel

My daughter went on a cruise, she couldn't make any calls or even have any internet while on the cruise , T-Mobile sent me a bill for $1566 , showing that she made calls , which she didn't because I couldn't even contact her while she was on the cruise , my husband had called them like twice before the cruise asking them to cut all international calls off  our account and they still send the bill saying she made international calls which she didn't,   I had call them and set up a payment plan for $356 monthly,which they agree to , the  first payment they got they restored my service in few days  they cut back my phone off saying I have to pay the entire bill before my service is restored, which is a trick they use to get you to pay like apart and the. They'll cut your phone back , we've been with them for many years , I asked them if I pay off my phone would it be unlocked so I can switch , they say no even if my phone is paid off they won't unlock it,  So basically even after paying off my phone I still cannot use it :-(.