I assume this is a broadband LTE modem? You need to make sure you have a very good connection to the appropriate tower. If you don't, then you will get some fraction of the maximum speed the device is capable of. What does the manufacturer documentation say?
What I actually meant was Modem's speed.not connection's maximum speed.
I connected it to a windows XP(I use 7 on my pc )pc .Then clicked connect and then pop up baloon came from the task bar and showed that it is 7.2 mb/ps.