SMSC vs. VoLTE on Murena 2 / Orange Polska network

I got the information VoLTE might not be available unless the network approves a given model of the phone of their network. Here is the situation with Murena 2 and Orange Polska network:

When 4G Calling is activated in the setting calling is possible and works OK. Data connection also works OK and the LTE icon is displayed next to the signal level icon.
Unfortunately, SMS is not operational. Sending messages fails. *#*#4636#*#* and refresh of the SMSC field on Murena 2 give the correct number:

The same operation on the phone that fully works on Orange Polska network (Xiaomi Redmi Note 10):


image

So, if this entry comes from the SIM card- it looks like Xiaomi doesn’t touch the string as used e.g. in the AT +CSCA command. The number itself is enclosed in double quotes and an address type field containing ,145 is retained. However, Murena 2 does something to these SIM card information so that *#*#4636#*#* command shows only the [ITU E.164/E.163 formatted] number without double quotes. Is this correct and should work without any issues?

Now, when the 4G Calling is disabled on the phone - the SMS works without any problems. Can it be that even when the 4G Calling is enabled it is disregarded and voice calls are dropped to the 2G network (3G has been switched off in Polska as far as I know)? How can one debug it to find out what the situation is? I am afraid that if voice calls do use 2G then any simultaneous data connections would slow down immensely (during the vaoice call - hopefully upon its termination the data connections are switched back to the LTE).

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