There are a variety of free messaging programs that can replace SMS and provide free texts between you and friends. The best way to take advantage of these apps is to have all of your friends on the same service. You'll then be able to easily send messages over Wi-Fi or mobile data without eating up your SMS allowance. Popular free messaging services include:  Facebook Messenger WhatsApp Kik Skype Hangouts Viber As long as you are connected to a Wi-Fi network, all of your messages will be sent and received for free. If you aren't connected to Wi-Fi, the messaging apps will use your mobile data plan to send and receive messages. Free messaging apps never count against your SMS allowance. You can use a free Google Voice number and the Google Voice app to send free SMS messages to any mobile device. Responses will be sent to your phone and to your email. You can sign up for Google Voice and get a free number at google.com/voice.  Sending and receiving SMS messages through Google Voice will use your mobile data connection if you aren't on a wireless network. If you have Hangouts installed, you can use it to send and receive Google Voice text messages instead of the Google Voice app. If you just need to fire off a quick text message or two, you can visit a text messaging site like textem.net or txt2day.com. These sites allow you to send messages for free to any number. You can't use these services to receive messages, but they can be useful in a pinch.

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Write a summary of the previous text in Vietnamese:
Rủ bạn bè cùng sử dụng chương trình nhắn tin. Sử dụng ứng dụng nhắn tin khi kết nối với mạng. Đăng ký Google Voice để gửi tin nhắn văn bản miễn phí. Gửi tin nhắn bằng dịch vụ trực tuyến.