Vodacom unable (or incapable?) to correct their mistake (gave me wrong data package)

I have had a terrible experience with Vodacom online regarding a data package that I was sold over the phone. I was phoned by a sales consultant and offerred a MyGig10 data package, which gives me 10GB data during the day and 10 during the night, for R199 p/month. However, they gave me a MyGig5 pacakage, which is half the data. I phoned to try and get it resolved: after quite some effort, I received a call back. They said that they listened to the sales call and that it was an error on Vodacom's part. I was told that it would be fixed by the following month. It was not fixed. It is now well over a year ago and I still cannot get it sorted out. I have spent hours on the phone and have been pointed in all directions. I have had tickets open at various departments, then they just close it and say it must be sorted out by a different department.

When I try to cancel, they want me to pay a cancellation fee. None of the Vodacom stores can help me, as they say it is through Vodacom online. I am extremely frustated by my situation and I have been a loyal Vodacom customer for a number of years now.

I have spent a fortune in topping up data and do feel upset about this as it is simply wrong.

I want to cancel this data contract, but it has been such a struggle. I will definitely not deal with Vodacom Online again - hopefully it is better going to the stores.