Big Fish - Cannot cancel subscription

We have been a member of Big Fish for a long time and we have rarely made use of the facility. For the last few months we have tried every possible way but cannot manage to cancel the service. Google suggested that I change the payment method to cash which I did at the beginning of last month but they still debited us last month. Can you please assist us cancelling this subscription, the exchange rate is bad and the monthly deduction is killing us. We cannot afford and do not require their services anymore but they will not allow us to cancel.