Poor customer service

Trying to resolve a simple query seems impossible. I pay them the agreed monthly fee every month. but suddenly I started to receive requests for outstanding fees. I called them to address the issue and all they do is to send me in circles between finance and retention. What makes this matter worse is that I was informed during the call that the device is out of warranty. In other words, they received payment and could not even confirm that the device is still working. Once again, they promised to call me back and needless to say, that still has not happened.