In most circumstances, the method of Port Forwarding can resolve these issues. Here is a guide on how to setup port forwarding for Netgear and Linksys Routers, and a general guide for all other brands of router.
With SIP there are only two ways to reliably receive incoming calls. 1. Place your SIP device on a public IP address, an example is a Netgear or Linksys ATA/Router combo connected directly<sep/>
RingCentral Online is a Web-based telephone and fax service for professionals and small businesses. It provides a toll free or local phone number and advanced features not found in traditional phone systems.