Always Flyin is correct, but the call sign could also be changed slightly if there is another flight from another airline with a similar callsign in the same airspace. AA 252 and UA 352, for example. ATC also changes it if they can't get a track started on it on the computer, but usually they would not use that on the radios. When the 8 is added to the front, the airline changed it; if a letter is added to the back, ATC altered it.