Airtel — 4g not working, shows 3g or e with roaming signal

I had upgraded my airtel 3g sim card to 4g before 1 week ago, but unable to get 4g network till date, my second sim is also airtel and works fine in the mobile. I had tried to contact airtel customer service, but no one resolved my issue, only answer i got is, its already 4g upgraded but not showing 4g even after changing network setting, remove n inster sim as guided by support team.
Pls fix it fast, i can't waste more time.