I feel your pain.
I was switched without warning from EE to Vodafone.
Now the following:
- Weak as hell 4G 1 bar at most signal at home location compared to 3-4 on EE
- Data transfer from 60-70mbps down on EE to average of 3-7mbps on Voda
- No Wifi Calling options anymore
- People can't hear me when they call me but can always if I ring them. This is random on incoming but like 80% of the time.
- VoLTE should now be an phone option on Voda network, it isn't.
Sent a new SIM (even though old was couple of months old), used 2 other models of phone with SIM - no joy.
Phone IS supported on Vodafone's network as they sell it direct (Xiaomi 10T Lite).
Pop an EE or O2 SIM in my phone and Wifi Calling and VoLTE lights up.
Been 3 months so far with this mess and looks like reverting to EE network again now until VM get kicked off.
It's with a VM agent, but still waiting.