Misinformation leading to huge bill ***

On 30 January 2015 I upgraded my Data package that has been running for more than 2 years from a 2 GIG bundle to a 10GIG day / night bundle to save costs as my account was very high. I was assured that everything was 100% sorted with regards to this. I started using this new account immediately with the understanding that it was active as it showed on my system. As I received my bill for February I was shocked to see that I was owing MTN R3145.09 (2642,58 MB) for the fact that I used \out of bundle rate"between 31/01/2015 and 07/02/2015. Nobody and nowhere was I informed that I had to wait until the 8th of Feb to start my new contract that I signed on 31 Jan 2015. I believe this is in breach of my contract due to misinformation and I would like to have my money paid back to me as soon as possible. I have been a loyal client now since inception of Cellphones in SA and I have paid hundreds of thousands of Rands over this time to have a dependable service. Suddenly I am treated like this! I have complained and only got a very vague reply stating nothing in particular. *** I need a reply soonest please.Your soon to be EX CLIENT! I am looking at ending my new contract now."""