Need to cancel a prepaid phone

Hi,

I have paid for 4 months for the cell phone prepaid plan that I have not been using.  Preauthorized transaction was set for my niece who was visiting last year because she had no Canadian credit card, or means to pay for the service.

I need to cancel this payment asap.

She left Canada middle of February, therefore

so far, I paid 4 x 45.20 dollars for nothing, and that’s almost $200.