FluffyChat - Open. Nonprofit. Cute ?
Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
TextMe - TextMe is a free calls and messaging application at both local and international levels.
Molly (Signal fork) - Molly is an independent Signal fork for Android
Talkatone - Android App on. Google Play. Stop paying for cell minutes, texts & landlines; Turn your iPad or iPod touch into a phone; Call/Text even in areas with bad cell coverage; Call/Text when travelling without paying for expensive international minutes.