BAD SERVICE AGAIN

This is my second issue where Telkom mobile(8ta) is increasing my phone limit / spending limit without my consent. I get 100 minutes free airtime and when my minutes are finished they normally tell me that I can no longer make calls . Last I had the same problem and they fixed it and it lasted for a while but now once again they allowing calls to go through letting me think I still have minutes left meantime they automatically increased my spending limit without me asking for it., my contract is R140 a month but you want to bill me R949 for increased spending limits without my consent. When will you stop cheating people out of their money? this is absurd! im breaking this simcard , just sad that I have to loose my number because of your bad service