TELKOM IS A ****

I have a contract with Telkom and I pay R199 EVERY MONTH they deduct it from my account,so for the past two months they just send me an sms that I have to PAY R410.10 and they have not sent me my invoice in the past two months to see why am I paying that much because I never even upgraded because I know I cannot afford it, I have been trying to call and everytime I call they just put me on hold and right now everytime I hang up, they send the sms reminder that I should pay R410.