Bad customer service

I have 2 contracts with telkom , the one for sim only data and device contract, on the device I was told my spending limit is 500 which is why I saw no reason to change it , and for the past months my statement was from 404 the highest would be R534. I got the shock of my life when I received an sms that my monthly statement for the month of may was R1356.12, I went what? How, then i remembered that some indian lady phoned me about 2 weeks ago offering me a credit limit of 1500 and I declined, because i cannot afford to. I signed in on the telkom app then I changed my spending limit to 0 and I also noticed on my bill that there is a once off subscription I knew nothing about. How can one pay so much for a contract that I only used to pay 209 . Then I phoned telkom I spoke to the consultant all he did was send me the statement and asked if I had access to the app so I can change my spending limit, and that on my device phone the spending limit has always been 1500 which I disagree with him and that on the sim only I need to log in and changed my spending limit which shows that it has been adjusted . But by who? How can a consultant make changes on my account without my consent. I am really upset