Hello Prejith,
What I understand If you did not complete your contract then it will ban on you for pending years let suppose you have 5 years contract and you have completed 2 years and you have left the job and 3 years are still pending from contract then they will impose ban for 3 years. Better option is if you can cancel you contract with mutual understanding and het noc or find other solution but dont go with this option go through below links
http://www.sheenservices.com/news/qatar-new-labor-law-and-working-contra...

https://portal.www.gov.qa/wps/wcm/connect/5f30f680423f8a149631df3cb857e4...