I am evaluating the MizuDroid app as an Android VOIP phone replacement.  We have been using Fonality on-premise server (pbxtra.fonality.com) since 2008, with great results.  However, I now have the need to eliminate some desk phones as we have a mobile Sales/Support staff that needs to use a SIP Smartphone device.

I have installed the MizuDroid app on my Samsung Note 8, setting the SERVER, SIP USERNAME, SIP PASSWORD.  I have been able to successfully Register the SIP device and make/receive calls, but I frequently lose the Registration and it is a struggle to get this connect again. 

I have also tested the Zoiper Android app, which does seem to stay connected a little longer, but has the same issue.  I would rather use MizuDroid, however, as I like the features much better.

Does anyone have any ideas?  Getting desperate!  I have reached out to Fonality, and everything is setup on their end, pretty straight forward.   

I will check (new IT Dept.). Do you have settings I can provide them? thanks!

I need the answer for my single question to be able to provide a proper answer for you.

"Is your SIP server behind NAT or on the public internet?"

With other words: what is your SIP server address?

Received your email and my colleagues will answer from there...