With Karbon card, you can have two phone numbers for OTPs.
Below are the steps.
Click on the card on which you want to add one more phone number for OTPs.
Click on the additional OTP button at the bottom of the dialog
Enter the phone number and click Next
Enter the OTP sent to the new phone number for confirmation
On all domestic card transactions, you would get 2 OTPs - one of on your primary phone number associated with your card, and one on the additional phone number you just added