Constant over-charging

According toy contract... my premiums are 349 for the first 3 months and 549 thereafter. I am in my 3rd month of my contract. Last month planet fitness charged me 549 instead of 349.... They asked if they should refund my money or credit my membership .. I told them to credit my membership. This month I was then supposed to pay 149 but instead they charge me 449. I call them and tell them to refund me this time cause im tired of the nonsense... They tell me my money will take 14 days to reflect. I then tell them to cancel my membership cause I've had enough ..the lady tells me I will have to pay a settlement fee. I tell her there is no fee that I'm gonna be paying cause they breached the contract aldready.. twice ! She tells me they can't cancel without a settlement fee. We argue back and forth and she hangs up on me. I'm definitely unimpressed with their mediocre customer service and inability to debit correct amounts.