unlock phone

I switched mobile services and had to deal with your terrible AI customer service, which never sent me to a live agent when requested.  Anyhow, I was given my transfer information and went through the process with the new service,  but was not made aware of the remaining balance. I went online and paid off what I understood was the device balance, but now it wants me to pay more money for some reason. I have already wasted almost $200 to get this process going. I just want the phone unlocked, so my child can use it. Figure your stuff out.