EE (UK) WiFi Calling still shows old iPhone in list

I've enabled WiFI calling on my carrier (EE in UK), but in the allow other devices it still shows my old iPhone which I sold. I remembered to disable iCloud/find my iPhone on the old iPhone, and erased it completely. I've toggled WiFi calling on/off, rebooted iPhone, airplane mode on/off etc but the same.

So why is it still showing an old iPhone in the list? I'm worried if I leave it on then the old one may interfere or get calls etc? I'm running iOS v9.02

Also on iOS 8 if you enabled WiFi calling, it disabled continuity. I used continuity for calls when I was in the house on my iMac, does it still do this? How does this all work with an Apple watch as well? I find it convenient if my iPhone is downstairs, and it rings, to be able to answer the call on my watch, is this still possible with WiFi calling enabled?

thanks