Disgusting service

I bought a phone at cell c whereas I had an existing data package with them, so I asked the sales consultant on the phone to downgrade my existing contract so I can afford the phone I took, he told me no problem and told me that my monthly installment was going to be R400 and something, so now last month they deducted R900 and now this month they deducted R800, so now I have been calling them since last month and no one is giving me a straight answer they just telling me that I have 3 contracts which I was not aware of, they only thing they do is to send me from one department to another instead of doing the right thing