Airtel — Airtel internet speed very low

Address:

sankalpa-3, newtown

Sir, i just bought the airtel postpaid sim from airtel store. for office work. i am living in one of the develop place of kolkata @newtown near axis mall.my airtel internet speed is so slow. i cannot work for single hour. its giving 3 mbps speed. when i bought the sim they told me that it will give approx 30 mbps speed. its my request please improve the speed of the internet near axis mall. its really bad.