subs not agreed upon

I have upgraded and I told whoever was assisting me that I want to stay on R250 top -up which we agreed upon. I am surprised that my bill for this month is R311.01, please advise what is the reason for that. I spoke to your customer service and Moipone from upgrade dept, all them couldn't assist. <br> <br> please be advised that I chose this amount of top up because I can afford to pay it