I am getting 4G speeds using LTE 1800 via Telstra. The Volla does not support Telstra's 3G band so the only way to make calls is via VOLTE. I did try an Optus sim which supports both 3G & 4G and it makes calls out of the box. I assume calls via 3G and data via 4G. The odd thing for me was the sa...

Long shot but worth a try, turn flight mode on, then off (resets network)
Had similar here in oz. Text works, cannot make/receive calls until do above.
If works, you only have to do it once after each start of the phone.
Works for me, hope works for you.

Cheers

Works with "no changes" on optus as well. Both optus & vodaphone use 3G 900mhz hence calls out the box. If you want to use VOLTE for calls you will still need to turn on/off flight mode once after starting. Telstra uses 3G 850mhz which is not in Volla's spec hence calls can only be mad...

I like you, tried all sorts of things including different sim slot until stumbling on the Flight Mode fix. I also cleared the cache in the dialer app plus in apn settings reset to default. Did nothing at the time but maybe worth a try. My sim does not display my number either. I don't think its your...

I am with Boost which uses Telstra 4G The Volla when using Telstra can only make calls using VOLTE so check settings - network - mobile - 4G calling is on and preferred network type is 4G. Then turn flight mode on, wait 10secs and turn off. If still cant make/receive calls try settings - system - ad...

Same for me. The following works for me.
Turn on flight mode, then turn off flight mode.
Now I can make/receive phones calls.
If you restart your phone, you will need to turn flight mode on/off again.
Cheers