Thanks D...that raises a problem. In English, an email and an app is deleted, you unsubscribe from an unwanted email, and you cancel a subscription and an account. Presumably that comes from the expression " To cancel a cheque". As you say ακυρώσω means to cancel and in Greek that is used for cancelling a cheque.
I was thinking more along the lines of cancelling something so that it no longer functions but it still exists, so it's not really deleted. It's there, but sort of put away if you will. In terms of glossary, the two verbs are different; in practice... well I guess it depends on the specific situation, like the examples you've given above.