Illigal upgrade still not Canceled after 2 months!

I've been struggling for 2 months to get an illigal upgrade cancelled! Every phone call ends with 'We will be in touch' and NO FEEDBACK is EVER given. I am still receiving invoices for the cancelled line even after multiple agents agreed that I will not be paying for it. Had to pay the amount to be able to still use my phone, was advised I would receive a refund, and that also never happend. Sick and tired of the poor service I've been receiving!!!