bad services

My aunt's decoders are not working properly and some of the channels do not appear like 161. we have taken them to our local dstv centre. when we arrive there, they test them and say that they are working fine which all well and good. but the minute we get home they do not work. we have asked that at least a consultant should come to the home and check them but no one has been. we have called mutlichoice on numerous accounts asking for assistance with luck there also. can some please call us and advise as it is unfair for the dstv account to be paid in full yet we not receiving a good service in return . an installer did com through and charged us. we still cannot view all the channels we have paid for. please advise on what is the next step as we are getting tired of paying and not receiving full services