From Voip Wiki
VoIP.com offers proprietary apps for both iPhone and Android. The downloads are free and setup is as simple as logging in with your MyAccount username and password. Just search their respective storefronts (iTunes and Google Play Store, respectively) for VoIP.com. If you're accessing this page from your phone, the iTunes link is here, while the Google Play Store link is here.
Both apps offer a variety of features. For more detailed information on these features, please choose the appropriate link below: