INVALID SMS'S

I keep receiving someone else's SMS's, up to 4 SMS's a month, about their account being in arrears. When I contacted DSTV they told me there is nothing they can do about it, they can only change the number on that clients account on his request. Never mind that I have been a customer of theirs for many years and pay my account every month. And, then the agent on the line still gets cheeky with me, saying that the fault is not on their side, and that I must go to a DSTV office to sort it out. We pay so much for DSTV and then get such bad service.