Phone not ringing when it has service

[Shuntfield]

Hello Everyone,

I have what seems to be a reoccouring problem with my phone Samsung Galaxy S20 Ultra.

It at this moment in time is in good coverage. It has 4x Bars of 3G signal and sometimes switches in and out of 4G where I am. If I connect to my WiFi then it swaps to WiFi Calling.

I have just had a text message, then a Voicemail indicator, where someone has been calling me all afternoon and left 3 messages.

I just collected them (on wifi calling), I then rang my phone from the landline, there was a long pause (where the network is hailing the phone from the cell towers it last saw it) then it dumped onto voicemail.

I then switched off WiFi, and tried making a call within service from the phone, again at 4x bars 3G and attached to HSDPA. The result was "NOT REGISTERED ON NETWORK"

I placed the phone in flight mode and then back out, then made a call to and from it, and everything was absolutely fine.

Any suggestions? - Recently had a new SIM card but it was doing that before I had the new SIM, it was in fact provisioned in this handset not that it should make much difference.

Thanks

Shunts...

[MI5]

Network issues?
http://status.o2.co.uk/

[Shuntfield]

@MI5 Yeah, I did have a look at that first.

Perhaps it could be something unrecorded, keeps happening though?

Shunts...

[MI5]

Fair chance I'd think.....

[gmarkj]

If it keeps happening, then download the my network app and report a fault.
Might also be worth trying a different phone with your sim to see if it is that.

[Shuntfield]

I think this is related to another issue that I previously had.
I think my SIM is mis-provisioned.
The problem is related to the SIM access profile in my Audi.
I have experienced this with the old car and old phone, and new car and new phone is now doing it. When I got a new SIM it worked fine for a while but now it's back.
It won't sign onto the 3G network, if you force it to 3G then you get no HSDPA service and you cannot make calls.
2G and 4G with calling is fine, but 4G will often play up until you restart the phone, and then it does the IMSI/TMSI handshake again.
Not sure what I can do about it right now.

Shunts