EE. Although I did once almost get banned from there.
In my defence they were being useless and unhelpful about DH's phone issues so I stood by the welcome guest and advised each newcomer that I wouldn't recommend EE as their customer service was awful and then signposted them to various other phone shops in the same shopping centre.
I thought this was perfectly reasonable but they took offence. I think they finally sorted the phone out just to get rid of me.