Azerbaijan’s country code is 994. Many landline city codes changed in 2014.
Payphones are very rare.
SIM cards typically cost from AZN5 for pay-as-you-go, with SMS messages costing 4q, calls per min 4q and data from AZN6 per GB. To buy one you’ll need your passport.
Mobile phones not purchased in Azerbaijan can be used for up to 30 days but after that you'll need to register the phone's IMEI-code through www.imei.az (costs AZN5) or at a post office (costs AZN5.50). To find your phone's IMEI code tap *#06#.