Issues with cancelling contract

I was contacted by Planet Fitness Sales Person from Queenswood gym on 18 Dec 2019 to notify me of increase in premium, told her I want to cancel my contract and she told me the contract will be cancelled and my final payment will be end of Jan 2020. Even told me that my daughter must call in to cancel her contract as well. Now receiving sms messages saying I didn't make a payment. Horrible service, been told if I have no proof on my cancellation, I am liable for the final payment (according to them) else will be handed over. Well, I will pay it so that I am not black listed by this horrible company with their *********** staff. But you are steeling from clients who supported you with their hard earned money for a year. Your have no moral value system. So glad I don't need your services any more and I really hope other people don't experience this side of your business. R480 might not be a lot for you but for a single parent it is food on the table.