Run away, then:
- return slowly, so you only have to deal with a few soldiers at a time
- wait until you are at a higher level, or get better equipment, to return
- wait until later in the game (a quest after you have been to the castle) and encounter one of the mages again (there will be a dialogue option about your character recognising him), after which the mind control spell will be gone
There is no way to get help for them right away, or tell anyone about the situation.