incorrect billing and poor service

I purchased the dstv price lock in feb. My price was suppose to be locked at R750 plus R83 for pause.record.rewind etc. But since then i have been charged R919 for March and about to be charged the same for April. I have not purchase any movies from box office. I contacted DSTV via live chat and they say they have no record of me buying the price lock. Quiet strange as DSTV themselves called me to offer this product. the live chat lady showed no urgenacy said that i will get a callback in 24 to 48 hours dispite saying that i am not available tomorrow. If this is how dstv want to play it then i must as well cancel and keep the explora since you say you have no record of it..........