I do not know where Telkom Mobile gets their amoun

I have a contract with Telkom mobile, which on signing on with them I made it clear to them that I want the amount to be debited to remain R130.00 nothing more, nothing less, and everything was going well until they decided to send me an sms to increase my limit which according to I rep**** on the sms with the no, the sms they sent me did not say I should call them but respond with a yes or a no, according to I rep**** and the sms was delivered on the 20/09/2015 they decide to debit my account with R289, when I called them they claimed they never received the sms, I put a complaint on hello peter and a lady called me on 30/09/2015, it was month end and I asked her to call me back which she never did, I wonder why, then today they decided to debit my account with over R777.00 after I called them on the 23/09/2015 and told them that I do not want an increase on my limits whatsoever, TELKOM MOBILE WHY ARE YOU TRYING TO FORCE AN INCREASE DOWN MY THROAT, what part of a contract don't you people understand.