Hi niks,
Lynn is right. When you paid for the trial, and logged into Paypal to confirm the payment, Paypal tells you that it is x.xx for the trial period and xx.xx per month starting on a specific date. It's easy to overlook if you don't read the whole thing, but it is there.
How do I know? I just did the exact same thing, but forgot to cancel before the trial was up and got charged for another month.
Ken MacKenzie