Billed incorrectly

I've taken out a contract with Telkom mobile just over a year ago, the contract was for 1gig data and R100 airtime monthly at R230 pm. Lately I've been billed between R500 and R600 pm for some reason. I've called the call centre on 18/3/2016 to query, REF number: ***3 (still no response on my case/complaint laid - out of 72 hr SLA), and according to them there was an increase on 29/2/2016 for R110 and again R379 on 27/3/2016 which was done without my consent... I do however buy extra data monthly which costs R39 for 250 meg and each time the consultant confirms that its a \temporary increase/spend limit\" on the account, by the looks of things, each month they are permanently increasing my limit. I want answers and I want answers NOW as I've been patient long enough, you are out of your SLA with my complaint laid (as stated above with ref number) "