There is an application called letter.

WeChat is a free application launched by Tencent on January 21st, 211, which provides instant messaging service for smart terminals. Wechat supports fast sending of free messages through the network across communication operators and operating systems platforms.

E-mail is an instant messaging software jointly developed by Netease and China Telecom, which can really chat for free, with unique functions such as free phone calls, high-definition chat voice, free massive emoticons, free short messages and telephone messages.

youxin is a social communication application based on the circle of acquaintances. Youxin itself is free. You can make free calls to national landlines and mobile phones, global friends with letters, free address book backup, automatic identification of friends with letters, etc.

Youxin is a kind of free communication software based on ultra-high-speed wireless communication technology, which is across mobile phone operating platforms, carrier networks and mobile terminals. Letters support global free voice calls between friends, free VoIP calls between non-friends, and national fixed and mobile phones. The letter itself is free. When using the letter to make free voice calls and direct dialing of VoIP, the traffic fee generated during the call is about 4K per second. When using the VoIP callback method, the traffic before the call is less than 1KB (there is no traffic fee during the call), and the traffic fee is charged by the operator. It is recommended that you open an Internet traffic package, and VoIP can obtain free call duration by "earning phone charges".

Yixin is a free short (colorful) message sending software based on mobile phone address book. Perfect integration of SMS and instant messaging, cross-communication operators and cross-operating system platforms, and unlimited free exchange of SMS, MMS and voice with friends. When both parties are letter users and online, they can easily communicate with their friends in real time without paying SMS and MMS fees, but only by paying a small amount of traffic fees.