negligence at its best

I asked my contract to be capped, as in when my data is finished then I recharge,but due to your staff members irresponsibility and your system malfunction and your lack of communication, I was billed almost a 1000 rand for data which I never used. I instructed the lady who assisted me that I am in no way going to pay for this bill, as I gave her the instruction to capp it,but she failed to mention for days that she was unable to do this due to their system being offline or something, the only time I was made aware of this was when my line got suspended,which still is.her attitude towards my query has reached a point of being rude, as I asked her feedback.On my query and her reply is 'as I told you, I will let you know '. ive asked for a reference or something to show that there is a legitimate query but nothing,ive asked for her managers details,phone just rings,my next step if this query does not get resolved is appointing a lawyer and lodging an officialy lawsuit.