Flipkart — Update the phone number

I want to update my account's phone number to a new one but I don't have access to the old phone number.
So when i tried to update the mobile number, the otps are being sent to both the new number and the old number. I have the new number's otp and account password, but as I don't have the old phone number, I can't enter that one's otp. Help me solve this issue.