As I already written earlier:
action=delete action is always delete here, and it does not matter what changes you going to do to an email account.
Open a directadmin page /CMD_EMAIL_POP?DOMAIN=domain.com in your browser and learn HTML code of the page to see what variables you can see (form elements, input fields and buttons). Also you may use Firefox to see what browser sends to Directadmin server on suspend/unsuspend an email account.
Before posting it here I've tested it myself. And sure if you try to call this API without unsuspend= or suspend= you will delete an email account. So test your code in a dev environment.