Dialpad - Switch is a cloud-based phone system built for Google Apps users.
Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs
TextMe - TextMe is a free calls and messaging application at both local and international levels.
3CX - Hosted PBX with CRM integration and mobile apps
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.