Hello ​@mihirkanani,
welcome to the o2 Community. After porting your number, you will need to register again with My o2. Have you already re-registered with the ported number?
Kind regards Bianca

I can login to my web using my ported number and getting login opt as well.

The o2 app cannot handle ported numbers. Until the problem is resolved, use the customer portal. You don't need to register again.

Good morning ​@mihirkanani 
There are currently a few challenges in our My o2 app with ported phone numbers. We are currently taking care of this and will hopefully find a solution for all affected customers very soon. Until then, please do everything via the browser, thank you.
Best regards

Kathi