Mi Xiaomi India — Mobile data problem

Address:

Chandigarh, Chandigarh

Sir I have redmi note 3I. bought this mobile phone approx 20-25 days before but from the very first day I'm facing mobile data problem. I have bsnl 3G sim but that doesn't work even I'm not able to search anything. Earlier I thought that, might it be sim but that was not so n I bought a new sim Airtel 4G but it has a speed of 2G hardly again that was not the case to sim problem it's a mobile data or its settings problem. Sir it's a request please help me out due to this I'm facing a great problem I'm college student n I have to work bt I'm not able to work on internet due to mobile data problem. Thank you.