that depends mostly on Traffic, Service provider, Signal strength and the place you live.
You can't get full 7.2mbps anywhere in Sri Lanka. But, you can go to a maximum around 3mbps (3 Mega bits per second / 0.375 Mega Bytes per second)
my dialog HSDPA speed with Huawei E220 modem:
1. Check signal strength.
2. Check that you're connected with HSDPA and not EDGE or GPRS.
3. Check that you have not exceeded FUP limit of your package.
4. Check that if other applications steal bandwidth.
5. Try with different modems and sims
6. Call ISP