This is very easy. Contact us easily in VIP Support and just write that you want to cancel. We will then cancel your subscription.

Yes of course. The more expensive your ChilledCoins lists are, the more coins you make. 

You can pay in any currency. It will show €, but it will be converted automatically when you pay.

If you get the 12 month membership, you are also in the next EA FC Season automatically from the beginning. Of course only until the 12 months expire.