Cancellation fee

I joined Virgin Active in January 2017, at Boulders Shopping Center in Midrand. I had to move to Bisho in the Eastern Cape in November 2017. There is no Virgin Active in Bisho so transferring my membership isn't an option. I called their call center today (30 November 2017) to cancel the contract and I'm told to pay a cancellation fee of R1600.00 ... I believe this request to be ******* (may the contract law experts of this country help me out here). This cancellation fee, I am told, is 60% of the sum of the installments for the remaining months of my contract (13 months). My question is: if I am up-to-date with my payments thus far, why should I be expected to pay for future months even when I will clearly not be using their services? How is it possible that I am contractually obliged to pay for services not yet rendered as is the case here? What legal footing does Virgin Active have here? What legal footing do I have? Is there any case law that reflects what a "reasonable" cancellation fee should be, in light of administrative and related costs a service provider may be entitled to in cases where the actual service has not yet been rendered? Legal experts please advise.