Reliance datacard Performance

Reliance data card was initially performing well, but as the days goes on its performance degraded.e.g: The connection never crossed 700 KB/S (approx 1400 KB/S earlier). that's why I dropped to my lower plan as to use it very less.Coz If It's a connection of 3.1 MB/S,thus at least it should show a speed of 2MB/S.very soon I m planning to change my carrier to some other n/w. Thanx...