How Can T-mobile get away with Stealing & NEVER resolve issues, only promising to have a Supervisor Call back but Never Do?

I believe I will have to now start the small claims in court. Could not transfer phones over called so many time and they told me they would cancel and refund my card. Never did and then sent me to a debt collector before they ever sent me a bill. They also sent a letter stating that they were going to send me to a debt collector but I received it after the debt collector called. We never were able to switch the phone lines over and never used data. still charging me. This company is horrible and would recommend not using them.