Depending on what type of management you have, some companies have an arm-twisting policy. They will insist they will suffer a loss in cost of visas, tickets etc. Don't give into that. If they still insist, you can take the support of the authorities or if you wish to leave quickly, bargain it out with them, Just tell them you will have QR 540 left in your pocket after you buy your ticket. Give then the 500 (40 riyals to go to the airport!) to get yourself your "freedom."