Your issues have now probably been dealt with but for what It's worth, here are my recent experiences.
I was "persuaded" to move from BT (which I was happy with, apart from the cost) to EE, as everybody will eventually be moved over to EE (according the person on the phone at BT). This was a very easy procedure and the transition was as easy as you could wish for (made the savings I negotiated worthwhile). I did have concerns about losing my BT wifi range extenders but the new EE hub covers my house adequately. I did worry about the BT Digital Home Phones but again - they all registered and worked fine...until yesterday.
The phones seemed to be able to "call out" (or receive calls) but the "voice" in VOIP was missing. No side-tone, just silence. I tried re-registering, checked for software updates and everything was up to date. I scoured the EE community and bingo , there was a solution - albeit not a 100% perfect one. Posters said to try and reboot the hub (ideally leaving it powered down for a few minutes). I did this and now the phones work...for the moment. Some posters say the problem resurfaces and others say they have had no more problems (touch wood).
If I could emulate Microsoft and "roll back" my broadband and phone setup to BT - I would do so in a heartbeat - despite the extra cost.
