It depends on the bank, some banks allow you to make a transfer without OTP.
Also, to confirm the transfer via OTP, you can first change the account owner's phone number by calling the bank. To do this, when talking to a bank employee on the phone, you need to provide the full details of the account owner (usually this is SSN, DOB, address, etc.).
Some banks allow you to change the phone number in the account profile, while others confirm the transfer by email.