Continuous deductions

I wanted to use Google music and signed up on the trial period. In order for me to do this I had to supply card details for when the trial period was up. I have since become unemployed and have not had a salary or any money in my account. There is no funds in my account yet Google are trying up to 6 times a day to take money that is not there. This is causing a fee from my bank for each failed transaction. This morning the amount was R169 with some cents. Please can someone get hold of me to stop this from continuing. I am not in a position to continuously pay a failed transaction fee.