Configurable softphones are not tied to any specific service and can be “configured” to any one of the many VoIP service providers that allow BYOD (bring your own device). All the phones I am listing here are capable of working with the most popular SIP (Session Initiation Protocol) services.
Configurable phones allow for a lot of flexibility when it comes to operating with various VoIP services of your choice. But along with flexibility comes complexity too.
Everyones PC system is different and the reasons you may have problems can be numerous and hard to identify or nail down - and not necessarily the fault of the softphone product you are using - it just may not like something about your computer or network configurations. If that's the case, try a different phone until you find one that seems to like your system configuration best.
From my experience, most VoIP problems are related to NAT Routers, Firewalls, and Codecs. Troubleshooting these issues can be complex and is beyond the scope of this article.
Configurable SoftPhones – for Free
While configurable softphones aren’t for the faint of heart, they do offer flexibility. The above list is only a sample of the many softphones available, today.