are you getting an invite to apply? if not, there is nothing you can do. Airtel in the last month fixed some loopholes like applying with an alternate number. Now the number needs to be on Airtel network. Even if it allows you to apply from a different network number, it will get rejected. They are tightening the requirements.
If you got 2 Airtel services at the least registered with your number, there are better chances for an invite/approval.