Develop text and voice verification webservice

We are looking for an experienced full-stack web developer to lead the effort on an SMS text and voice verification web service that would manage the available phone numbers across all registered users for text/voice verification. We plan to use a hardware SMS gateway to provide a pool of actual SIM card-based phone numbers which the web service will manage/control using the provided REST API of the hardware SMS gateway manufacturer. The initial POC can be implemented using a couple of phones with multiple sim card support.