EE's contracts - in common with most of the UK telecoms industry - are not fixed term ones that end on a particular date. They are ongoing "rolling" contracts with a minimum term. Until & unless you explicitly give 30days notice of disconnection, your service and billing continues as normal.
Yours is now a tricky scenario - ordinarily the standard procedure is to contact EE CS by phone or letter, for the account holder to give cancellation notice, I don't see anyway for a third party to give this notice on your behalf. The Armed Forces covenant allows for subscriptions to be frozen for upto 12months in the event of an overseas posting, but there is no mention of "spouse or third party to cancel contract" - which contractually, could be problematic.
