Flipkart — Want to change my number in my account

Wan to change mobile number in my account.
i have lost the old number and when i try to change the number its asking to enter the otp from that lost number how could i enter the otp.
this is my old account and i want to use it future because its has my all kyc done and also eligible for credit card and pay later but because of that old number i am not able to do anything.
please change my number.
old no.-- [protected]
new no.-- [protected]
mail id. -- [protected]@gmail.com