Not receiving 3g speed

Location/place: Lucknow

Name of company/service: Bsnl

Sir,
I recently bought 3g bsnl sim whose number is 7376965147. The problem is that it is not giving promised speed of 3.1 mbbs and I am still receiving speed of 2g sim even after I recharged it with 3g data plan of Rs 1500. Kindly look into the matter.