You must have been in their bad and naugthy list. QA keeps full file on all their staff, they keep every details of Bads and Goods. If you had more Goods on your file, they will help you and treat you nice, but if you were on their Bad side, all hell will drop on your file and future opportunities in Qatar. For them, to even ban you, you must reflect and look back what you have done to piss them off.