Overcharging after putting BAR OR LIMIT an account

I am a very irate and unhappy client of Cell C at the moment and am utterly disgusted by your misleading take on consumers everywhere. My contract sim has been misplaced and subsequently ******,without my knowledge, however that not the problem - the PROBLEM IS I HAVE 2 CONTRACTS WITH CELL C BOTH HAVING A BAR OF R50.00 USAGE ON IT. then I get a bill for ALMOST R900.00 this month which was then deducted from my bank account, I WANT TO KNOW HOW COME YOU GUYS ALLOW PEOPLE TO GET BILLED OVER WHAT THEY HAVE ASKED AND REQUESTED NOT TO DO... I HAVE ASKED FOR A R50.00 LIMIT CAUSE I DO NOT EVEN USE THAT SIM CARD REGULARY AS I ONLY USE THE PHONE CAUSE I PREFER PRE-PAID,YET YOU GUYS HAVE ALLOWED THIS TO HAPPEN THAT MY BILL HAS GONE ABOVE MY BAR/LIMIT WHICH I HAVE ON MY CONTRACTS, THAT IS NOT THE WAY TO DO BUSINESS. AS YOU GUYS KNEW WHAT MY BAR/LIMIT IS ON MY ACCOUNT AND YET YOU STILL ALLOWED TRANSCATIONS EVEN WITHOUT SECURITY CHECKS TO BE DONE ON MY ACCOUNT HOW AN YOU DO THIS? EVEN WITH CELL PHONE BANKING YOU HAVE SECURITY ,MEASURES IN PLACE THIS SYSTEM OF YOU GUYS ARE TOTALLY WRONG AND I THINK YOU NEED TO RE LOOK THIS AND I DO NOT WANT TO PAY FOR THIS WHAT HAPPENED TO ME WITHOUT MY KNOWLEDGE