Virgin increase their rates without consent or permission

Virgin active Gateway have debited me R525 for my gym membership for a long time now and upon questioning my contract length a few months back I was told that my contract was not due to end for a while. A days ago a lady called me with an offer to gain access to all the clubs for R900 or so and she seemed very surprised as to how much I was paying as if it was not the correct amount, I picked up on her tone and didn't take the offer. The very next debit has been for R725 and upon calling the club I am told it is their yearly increase.

I would like to know if inflation warrants a R200 increase and secondly does my contract state that the price can be changed at any point with out my consent?

I am almost certain that the price was changed to correct an error made years ago and to cover this up it was changed with out my consent thinking I wouldn't notice because it is a wealthy area. This is a case of breach of contract and I am certain that all the funds I have ever paid are due back as a result of this. Nevertheless I will post this and follow the necessary steps to get assistance as I know this is unfair and wrong.