I suggest that you go to the relevant department of the Municipality and show proof that you are leaving town.
In the meatime, isse a letter to the landlord stating "further to my verbal advice, I shall be leaving Qatar on XX/XX/2008." If you gave the proper verbal notice timewise mention it in the letter...however, you may need to pay a month from the date of issuing the said letter.

Note in the letter to provide all pending postdated cheques.... if they fail to respond or respond negatively, call and tell them that you will be taking the matter up with the tenancy department of the baladiya...this may move things...if not go and see them, they should help to see you get out of the lease....