SMPP User Account

I need help in providing an SMPP interface to my users as show in scenario below. An assistance is appreciated.

I think that scenario is not possible. PlaySMS does not speak SMPP. If I understand correctly you are trying to use PlaySMS as a billing system by placing it between your clients and the SMS Provider. The blue box SMPP server will have to connect to the PlaySMS through the API (Webservice)