By default on the SysAdminMan A2Billing template the customer signup page is disabled. This is because anyone using A2Billing to provide call services to the general public should consider very carefully any fraud implications. Call providers are definite targets for fraudsters and any customer should be closely vetted to ensure they are legitimate.
There are many stolen credit cards and PayPal accounts in circulation. You should absolutely not allow automatic signup/activation.
So, with that said, how do you turn on the customer signup page? In A2Billing go to SYSTEM SETTINGS / Global List / signup and set ‘enable_signup’ to ‘yes’
You should now be able to go to – https://vps_ip_address/signup.php