I WANT MY MONEY BACK

I took this medical insurance in November and December they deducted the premium. Then in January they double debited my account. When I contacted them the lady there told me that the double debit is to balance my premium as they deduct in advance. On the 31st I sent them an email informing them to cancel my membership effective immediately and to refund my money back. They gave me a run around and now they are telling me how they cannot backdate the system. I want my money back I don't care about what your system can't do. I have worked for an insurance and medical aid company and I know that you can do what is right. This is the worst medical insurance ever. I WANT MY MONEY BACK I don't care about cover, I wasn't even covered for anything because of the waiting periods so it was useless either way