https://wiki.sangoma.com/display/CONNECT/Introducing+Sangoma+Connect

https://meet.sangoma.com/

https://wiki.sangoma.com/display/CONNECT/Installing+Sangoma+Connect+for+Mobile

1. Mobile Device → App → Settings → Reset Application
2. FreePBX → Resend Invitation
3. Mobile Device → Open E-Mail Invitation
4. Mobile Device → Click Login Link
5. Mobile Device → Open App
6. Mobile Device → App → Give All Permissions (if prompted)

https://www.counterpath.com/product-comparison/

https://www.sessiontalk.co.uk

The free version works well.

Additional paid business features:

• Transfer Feature $3.99

• Free
• Android 4.0+
• In Google Play market

http://www.grandstream.com/products/ip-voice-telephony/softphone-app/product/grandstream-wave

• Free or Paid
• SIP and IAX

https://www.zoiper.com/