Ripoff by Mtn South Africa

had a Data contract with MTN for the past 24 months , when the contract was due to expire , i received a call from MTN call center advising me that i'm due for an upgrade in April however if i upgrade now there will be no cost and that the benefits will be more as i will now get a better package. i agreed to the new deal pending me receiving confirmation of the offer which i didn't get to date. To my surprise i was billed R799 at end of Feb instead of the R210 which was my normal monthly bill. i queried this at the MTN store and i was told there is a migration cost which i was charged but this i didn't agree to and also i was promised by the Call center agent that there will be no additional cost for me to upgrade. Secondly i still didn't receive the confirmation of the new offer as promised. This is a ******* by MTN