Vodacom's lack of working internet connection

We are currently on a data plan with Vodacom. initially the upload and download speeds were fine, but after a month or two the connection became stuttered. Continuously going from working ok to not being able to load a basic website. Went into Chats Vodacom in Waverley plaza where the contract was signed and complained about it. They said that they would reset the setting so that the sim can synchronize again. It worked for a week and the same problem came up again. Went back to them, same story. I have now been there 3 times for resynchronization. Last time they had me pay for a new sim card and do a sim swop. Now I have no connection what so ever.

This can not be what I pay for every month? At this rate I would just like to cancel my contract as Vodacom is not keeping to their end of the contract by delivering a service that I am paying for.