Vodacom fails to honour customer's request

I transferred my contract from a corporate account to my private capacity.Having been recently retrenched and the first time owner of a cellphone contract,I visited Vodaworld in September.Whilst sorting out the paperwork,my instruction which was written on the contract as well as discussed and confirmed by the representative was that my credit limit should not exceed R1500 all inclusive.This in my understanding meant that at no point should my bill exceed this amount.This was done by to ensure that I don't run the risk of any financial burden.2 weeks later my line is softlocked due to data usage.After contacting customer care,I discover that my account was sitting at R3500 with the new credit limit not being captured on the system.The agent tells me that I was meant to set a call limit and a data limit.After much back and forth dispute,data services agrees to investigate and get back to me in 7 days.Failing to commit to their promise 2 weeks later my line is still softlocked and my account is now on R5888.I receive no feedback despite my numerous calls.Based on my affordability I set a credit limit which Vodacom was meant to honour,this is not acceptable and I refuse to pay!!!