To cancel you should follow the advice laid out here: https://ee.co.uk/help/profile/leaving-ee/leaving-ee-what-you-need-to-know
In this case you would need to call and give 30 days notice while requesting to be switched to Pay As You Go.
Unfortunately as you are now outside the UK, once this goes through (after the 30 days notice) it will require activation on EE's UK network before allowing the PAYG SIM to function correctly. This process should ideally have been undertaken before travelling abroad.
You could potentially post this SIM to a friend or family in the UK to allow them to put it in a phone and activate it, before then returning this to you.
