Most of the voip provider that provide unlimited voip calls always have a usage limit on it…read for the smallest font terms and conditions at bottom of the page.So the best way to call unlimited is to invite others to use same voip provider as almost all the voip provider have policy of free onnet calls(on same company voip network).
Now some of these voip providers are paid while others are free while it would be not appropiate to ask others to select same paid voip provider as there are many possible reasons for choosing a particular vsp(current setup, low ping, low rate to a particular destination) on the other hand free vsp won’t be reliable enough(with zero support) and no outage notification.
The only reliable and free way is to use direct ip2ip calling with dynamic dns. For a direct connection between 2 Voip Adapters you need to have a router having Dynamic DNS client on both ends. Dynamic DNS basically stands for dynamic domain name system and having a DDNS client built in will allow you to have a domain name inspite of
dynamic IP addresses which is a necessity for point to point calling on a Voip adapter.
The steps you will take are as follows:
1. Configure your ATA (or Voip Adapter) to accept IP calls. By making allow incoming calls to yes(in Linksys ata).
2. Make your router to allow SIP calls(port forwarding) through your router firewall.
3. Next u need to go to www.dyndns.com and create an account there. While signing up u need to choose the domain name of ur preference viz. abc.dyndns.org etc this will be the domain name that you will put in the domain name field in ur router. Username & password will be same with which you have created the account.
4. Now you need to choose dyndns as the DDNS server in the router. You need to fill in the details and enable the client in the router and then save & reboot.
Now anyone could call you just by making a dial plan that will forward to sip:username@abc.dyndns.org where username is your existing voip provider username that is currently feeded in ata. Everyone calling you via this way will be directly calling you without any voip provider involved.