A phone-on-file opt-in method is described. A phone-on-file opt-in request is received at the billing server including a msisdn and a merchant supplied unique consumer identifier. The billing server confirms the phone-on-file opt-in with a consumer device and records a phone-on-file opt-in status as active if the first phone-on-file is confirmed. A charge method includes receiving, at the billing server, a charge API call from a merchant server including at least one identifier and an amount, determining a phone-on-file opt-in status corresponding to the identifier at the billing server and transmitting a request to charge a user account to a carrier server if the phone-on-file opt-in status is active, but not if the phone-on-file opt-in status is inactive, the request including an amount corresponding to the amount received in the charge API call.