On air tv are lairs

Hi my husband and I received a call from on air tv for a offer on the explorer wish we took it was installed but it was faulty . When they phoned again to find out of everything was okay we told them it is faulty. The technician told us its okay we can keep that one he will replace it with a new explorer and will cancel the old one so we dont need to pay for that one its our gift . We received the new one . With our first instalment we noticed that we are paying for two decorders . We have been trying to get hold of them for almost two months to sort the problem out but they simply just not giving us a ear . We are still being billed .