For security purposes, PayWow has mandated two-factor authentication for every business. So, while signing up, you'll be asked to verify your mobile number to which you'll receive the verification code on all future logins.
In case, you want to update the mobile number linked to your account, you can do it by navigating to My Account >> User Profile.
Adding to this, if you're unable to access your mobile number, you may contact our support team for accessing your account.
Please note that standard text messaging charges may apply.