Poor customer service

I was contacted by sales agent who advised me that I’m using one of the old multichoice decoders they are upgrading them , I need to change because they will no longer work at some point I agreed she told me I will receive a decoder from on air which will be delivered free and they will be an Installer, I will start paying as soon as it goes live ,they delivered the decoder In an incorrect address , they have been trying to deduct on my account and I’m told I have a contract for 24 months which was never disclosed on the initial call ,when I tried to cancel they said I cannot cancel and 7 days has passed ,I’m afraid this is going to ruin my credit score and would like to be assisted to cancel this the decoder is still in the box and has never been used