Iphone inbound calls intermittently failing

[GeorgeO]

my wife's Iphone 12 mini (IOS 16.5 )  recently started having problems with some inbound phone numbers connecting but then dropping with 'Call Failed'

Not all numbers have this issue .....texts work fine and most inbound calls work 

Any pointers as to why some inbound calls would fail to connect?   The signal strength at home 

is quite low (1 bar).   We've always been in a dead zone for some reason.

Outbound calls don't have a problem.

cheers

[GeorgeO]

thanks .....my problem is the option 'mobile data' does not appear.  Under 'bluetooth', the option is ' Cellular'  

tapping on 'Cellular' I see option for 'cellular data' .  selecting 'cellular data' I have the option of 'off' or 'primary' which is the Public Mobile SIM.    The  Esim is not selected

cheers

[softech]

@GeorgeO 

check if this is helpful

https://www.helpforsmartphone.com/public/en/apple/iphone-12-pro-max/ios-14/guides/24/Switch-between-...

[GeorgeO]

thanks for the quick reply.   Sorry for being so dense but I don't see any of these options on her Iphone.

I see settings=> cellular data   option Primary>

default voice line primary.

on Cellular data    options are 'Off'   or  'Primary' which has been selected.

The Iphone has an ESIM installed but it is currently turned off.

[softech]

@GeorgeO   your wife phone could already been using VoLTE, not sure if it is a VoLTE issue

Check if you are using VoLTE

When she makes/receives calls, check if the phone screens showing it stays on 4G before, during and after the call. 

Later,  can you please change the phone to 3G Only and see if the voice is working any better. 

Settings->Mobile Data->Mobile Data Options->Select Voice & Data , then enable 3G

Leave it that way for a day or two and see if it works any better