Regret signing a contract at Virgin Active

I signed a 2 year contract at Virgin Active Cradlestone, in November 2018. This contract states that I have monthly installments of R399.00, for a commitment period of 24 months, which is payed via stop orders. Now after 10 months of signing the contract, they have increased my stop orders to R539.00, without informing me, and without my consent to increase my stop orders. I tried phoning head office twice, and both times they hung up. I then went to the club to speak to the consultant who I signed the contract with, to find out why they have increased my stop orders without telling me or asking any consent, as the contract clearly states that I have to pay R399.00 for a period of 24 months. The ill-mannered sales consultant said that she'll get back to me the same day, which, like expected, did not happen. When she phoned me today she very rudely told me "that is just the way it is", and after I told her that I cannot accept it, especially because the contract VERY CLEARLY states what is expected of me and what i have to pay, she became very disrespectful, impolite and ****y, continuing to insult me. The way Virgin Active and the sales consultant went about this is very ********* and rude. Their clients should be aware of the way Virgin Active does business and how they deal with their clients' complaints or queries.