I am user of Airtel from last 2 years and do recharge from recharge shop.
I latter started getting messages from airtel to download a mobile app for recharge which I did.
I happen thrice with me when I recharged my money debited from my credit card but recharged went unsuccesfull.
When I call customer support they ask me to wait 7 days for refund. I did same recharge using other app that heppen more quikly than Airtel aap.
Never use Airtel app for recharge.
It is good to track your mobile balance or internet data, not for recharge.