Monotronics won't refund money after they recived letter saying we cancel Dallas Texas

we were moving,a company ( Apxalarm)came to the door saying they were upgrading our system We thought they were monotronics ,which we had for a good 10 years.turn out it wasn't our alarm sytem.by mistake i had signed up for five year contract. so had to call monotronics to cancel they said to send register letter to dallas. to cancel our old system. wich we did.they are still taking out money out of our account two months after letter was send, sign for. won't refund their mistake, said they did not recive it, we have a sign recipt from post office showing they did. we have been taking advangate of both both companies now. one we can't cancel because of being miss lead into beliving we were dealing with our company and our company now charging us for a service they are not providing.

Robert
San leandro, California
U.S.A.