Dubble contribution

We had contacted Momentum 2 months ago, to go on a lower option, we have been advised that they already had change of option, the reason for our change, I started a new job and my salary was cut, so we then told them that we can't afford them anymore, and they've cancel it. I didn't had any funds in my bank so they couldn't get any contribution. So this month they took R7494.75 and again there was no funds into my bank account and now I'm into a minus on my FNB account. I phoned them today and this \friendly"lady said I have to phone the bank so they can reverse the money"