Cloud Softphone is described as 'White-label softphone platform where you can create, test and deploy mobile and WebRTC endpoints in less than 30 minutes' and is an app in the Social & Communications category. There are three alternatives to Cloud Softphone for a variety of platforms, including Android, iPhone, Mac, Online / Web-based and Windows. The best alternative is Zoiper. It's not free, so if you're looking for a free alternative, you could try Telephone.
Telephone allows you to make phone calls over the Internet or your company network. If your phone line supports SIP protocol, you can use it on your Mac instead of a physical phone anywhere you have a decent network connection.