If you submit a cancelation request through the client area then your PayPal subscription will automatically be cancelled (if you have one). Otherwise if you would like to cancel it before then please follow these instructions to cancel your PayPal subscription:
  1. Login to your PayPal account.
  2. Go to your Profile, and click My money.
  3. Click Update beside 'My pre-approved payments'.
  4. Cancel the agreement for 'IVPN LIMITED' in the 'My pre-approved payments' section.

Alternatively you can follow the instructions on PayPal's website.