I am using Tele2.
I installed Lineageos nightly on two of my phones and in the beginning I could make volte calls, but yesterday(I thinK) it dropped to 3g during calls.
I have checked in my pages at Tele2 and they have blocked the pixel 3a to use volte.
I am able to make volte calls on my pinephone using Mobian. But it is red-listed on my pages on Tele2, this means that the pinephone will be blocked 1 february 2026, I guess, it could be dropped 9 december too.
I heared somewhere that hey are doing the same thing in Australia, I have little to none information for the rest of Europe, how they implements volte emergency calling, or how they rules out the unsupported devices.