Calls - SIP VoIP Softphone is a simple and free softphone that allows you to make calls over Wifi and 3G. The app supports both UDP and TCP transports, as well as g711, g722, g729, GSM, Speex, and iLBC codecs, making it a versatile option for users. Additionally, it supports sending DTMF and call transfer for added convenience. One of the standout features of this softphone is its background service, which allows users to receive incoming calls even when the app is running in the background.

Moreover, the app offers high performance and supports UDP, TCP, and TLS transports, as well as g711, g722, g729, GSM, Speex, iLBC, and OPUS codecs. It also supports sending DTMF and call transfer, and allows for calling over both wifi and mobile networks. The app provides background, foreground, and push notification services, ensuring that users never miss a call. Overall, Calls - SIP VoIP Softphone is a reliable and versatile option for those looking to make free calls over the internet.