bought airtime and dont get it

every time i buy airtime at Mr Price on online i dont get it and when call the call center for help they dont help. they refer me to cell to cell but i bought airtime at Mr price not cell to cell.Last month i called cell to cell and they said that there is no billing for airtime as they cant sent the vouchers but now the billing reflect airtime which i never got. Why should you buy airtime at /mr price online or at cellphone ussd and call the other company for authorization to get airtime . Mr price bill customer for nothing and am not happy about their service.