I have been using Zoiper for well over a year on my LG Leon H345 Andriod (Lollipop, v5.11) phone. I am also a Zoiper subscriber and the President of DigiLink an ISP that offers Hosted PBX/VoIP service. I actively promote Zoiper as a practical solution to businesses that want mobility on the HostedPBX service.
One vexing issue has been that I have been unable to get Zoiper to work properly with an external bluetooth audio device - it is very frustrating that this fundamental function hasn't been fixed in the last year and doesn't seem to be getting the attention that it deserves.
It is a source of major frustration to receive a call on Zoiper while I am driving as I have to answer and then hit the speaker phone tile three times in order to be able to hear the other party on the built-in speaker of the LG. Why 3 times - 1 to divorce the LG from the external bluetooth audio device, but then still no audio - anywhere, a 2nd time to switch the speaker phone off and then a 3rd to turn it back on - finally I can hear the caller who can also hear me cussing the entire time that I am dealing with salvaging the call!
Come on on guys! Zoiper would be a great VoIP app if it would just properly integrate with external bluetooth devices! PLEASE get this sorted out ASAP - its long overdue. Please don't tell me that the Android Zoiper app is in Beta! First you are accepting payment for the app and 2nd - this problem should have been one of the highest priorities to fix!