24 MONTHS CONTRACTS WITH CELL C

I took out a contract on 26 March 2014 with Cell C for R59.00p/m per phone for 24 months. Since last month they are deducting more money without any notification what so ever. Yesterday (2015/04/01) I spoke to one of the ladies at the customer call center and she told me that someone will contact me regarding this matter and till now no-one phoned me. I phoned again today and spoke to another lady that was very rude, that told me that Cell C can change the rate and that they have send me a message which they didn't. I would like Cell C to fix this matter asap.!