Massive data bill after contract was meant to end

My 3g contract expired on 03 December 2015. A week before that I contacted the call center and a consultant told me I would not be billed again after that and the connection will stop once the sim switches to prepaid. <br> <br> I then registered online because I noticed the sim was still connected to the internet. I then saw an unbilled invoice of R1800! This is after I was told the data would not keep running once the contract ends. This is a huge amount compared to the normal monthly charge of R79! This was all because the consultant told me to use the 3g connection until it stops connecting. I noticed this on 17 December and logged a query with MTN who didnt bother to respond, they just closed the query (As I could see on their online customer portal).<br> <br> I just called customer support now and a very helpful consultant explained to me that the previous consultant had not put through the cancellation on my contract as requested and the contract is still active. She did however put it through and has said I will need to wait 7 to 10 working days for it to be properly terminated. She also advised that there is still an outstanding bill of R1800+ to be debited by the end of January 2016! Plea