Al is an unseen character in GTA V and GTA Online, the only way you can discover his existence is through dialing an number otherwise unspecified in the game. Dialing the number 346-555-0109 into your phone in single player or online, will give you the following message:
"This is Al - I ain't available. Call back another time."
Al has a gruff voice and seems to be middle aged. It is unclear at this time if Al was a cut character, or if he is a character planned to appear in future DLC.