If you get a message that ‘user already exists’ it could be related to an old account that was not removed from the system, a mistaken number entry, or a recycled phone number.
Contact PayByPhone Support with the phone number, and we can look into this for you.
In the meantime, you can also transact in guest mode. (Click on 'continue without an account')
PayByPhone Support Team: https://support.paybyphone.com/hc/en-us/requests/new