Billing nightmare

I signed up with Vox in March and an incompatible device was sent , escalated this and I was promised a refund in the midst of sending the correct one , the correct on was then sent and installed in April and I was then billed again. To my dismay the call centre does not have a clue of what they are talking about , took me over 10 calls to be advised I will not be debited for May, for them to debit account again. Another escalation was sent and no response whatsoever- I need my money back or I'm cancelling