To set the scene and provide context. We have been using VitalPBX 4.0 for a while now, with no reported issues by any users. everyone can make and take calls successfully with two-way audio using VoIP Yealink handsets, Vitxi WebRTC and the VitalPBX Connect Mobile app. One of my colleagues had to call into the office from his mobile (a Xiaomi Redmi Note 8 Pro), when we answered his calls they lasted 6 seconds and then dropped. Each call would have one-way audio, he could hear us but we couldn’t hear him. Normally an issue like this would point me straight to firewall issues, but how could that be with all the aforementioned working just fine? I then asked him to disable VoLTE (Voice Over LTE) on his mobile and try again, he can now call us with no issues with two-way audio and everything.
If we call him though, the goes through two-way audio and everything and we can keep the call open as long as we need.
We do not know if this is just his particular mobile or his mobile operator causing this, has anyone had any experience with this kind of issue?
Paul