Eligibility for ITA promotion?

I have a total work experience of 3.8 years (fully in TCS) and my last 3 bands were A,B,B. I have been asking for my SE it ITA promotion for last 4-5 months, but my manager says that I am not eligible yet. Many friends who joined with me, got promotion already. Does band affects in this case? Can anyone please help me on the eligibility factors?