Dstv prize lock fumbles

I have a disgusting service from multichoice prize lock which I even complained here on hello Peter, I was offered dstv prize lock special of R550 per month for 12 months but I never received that decoder. After complaining on this website they tried to help but they failed and now things are worse than before as I am now billed R1380 instead of 519 which is my normal subscription but I don't know why I must pay that money when I never get anything as promised please I need help