BA has three call signs
SPEEDBIRD which is used on the vast majority of flights. SHUTTLE which is used on the "shuttle" services to MAN, GLA etc. The last one is fairly unusual but is SANTA which is used on the "santa" flights..a quick blast round the skies were the kids get to meet the Santa and some presents etc.
Many more callsigns used by franchises and wholey owned subsids around the world (British, Speedway, etc) but the above are the three used by BA mainline.