Unfair placement

Good day.I've got a question.I've been under the army contract for 2 years as an MSDS.now they are saying I can't sign a contract and I have to be in the reserve force.my question is,is it fair?shouldn't they tell me 6 months prior signing?now I can't go forward or apply for a new job.is in unfair dismissal?should I seek help with this?..will appreciate your answer.thank you.