Can I complain if my contract was not completed but the owner chose to repatriate me due to change in trade of vessel ? I am a 3rd officer, there were two 3rd officers onboard before but due to change in trade of vessel one had to sign off.

You need to give details , how many months your contract, did it had plus , minus e.g 5 months plus minus one.  When you signed off.

But I suggest in present market scenario better to get job back on another company vessel and avoid all this.