Yes you can.
Either put the sim into a phone and use the STAC option on the guide below (will only work if you just have the iPad), or call o2 customer services.
Guide: Cancelling Your Contract
Guide: How to find help & contact O2
Edited to add correct links.
Please note, this is not customer services and we cannot access your account. Do not publish personal details (email, phone number, bank account).
Link to our guide on how to contact them can be found here
