Hamad does have Zyban. At a very cheap price also beacause they are distributing it as part of a national smoking cessation campaign. One month supply cost me only QR 44.
Anyway, the number to call is 4391177. Ask for an appointment at the Smoking Cessation Clinic (it is in the outpatient building at Hamad).
It's really simple. You go in for the appointment and walk out with the meds in hand.
Good Luck!