The invention provides a method of processing transactions with a billing server, including receiving, with the billing server, a transaction request API call from a merchant computer including a msisdn, transmitting, with the billing server, a transaction request response to the merchant computer in response to the transaction request API call, including a transmission ID, receiving, with the billing server, a payment authorization text message from a consumer device at the msisdn including a transaction ID, determining, with the billing server, a match between the transaction ID in the text message with the transaction ID in the transaction request response and if a match is determined between the transaction ID's, transmitting, with the billing server, a charge request to a carrier server to charge an account on the carrier server corresponding to the msisdn.