Band rejection methodologies

It so depressing to get a C band after having been a good performer since long. The following were my bands from the last last 4 years A, A, B, A.

Apart from grievance and band rejection do we have any other way to approach for band change and is there anyway that i can request for hr change for the grievance? I see my hr assigned was very very biased and was behaving as if he is their lawyer when I had protested against the bad rating.