QUOTE(Ngto @ Aug 10 2018, 10:00 AM)
Thanks. My phone is Lenovo P2. It support voLTE but maybe not recognised by Unifi.
Telco can check your phone model before allowing you to connect to VoLTE network (as well as other services), there are few ways to disable this checking, just browse XDA and you'll be able to find them (if you are a tech-savvy person la

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QUOTE(wilson1stop @ Aug 10 2018, 10:28 AM)
I was tested with both VoLTE phones in differences towns/cities, maybe is your area CELL TOWERS not support VoLTE?
Example my hometown was not showing HD calls, but when calling in city my phone showed HD calls and it's very clear.
Most likely, so far I am able to use VoLTE on band 5, 38 and 40, maybe certain places don't have VoLTE yet just like what you said, but VoLTE is quite buggy on my Note8, sometimes need to switch on airplane mode and switch off again to connect to VoLTE on same location and tower
QUOTE(LeonTan @ Aug 10 2018, 10:32 AM)
erm....
it seems not many ppls able to volte for their phone, maybe like that you say, only specific models able to get volte
maybe I stick to 3G mode until I change my phone
unifi mobile is my 2nd number so not really urgent

Only popular models get the support nowadays because VoLTE and VoWiFi (WiFi Calling) both require extra settings from device manufacturer and telco to ensure these technologies can work on their devices.