Three mobile, does anyone have any experience dealing with this issue?

So I went and jumped ship from Vodafone after many many years and went to Three today. The changeover was a bit of a disaster, the sales person accidentally deleted phone before she should have so ended up locked out of iCloud, not everything backed up and there for over 3 hours with a 4 month old baby dying to go home. Eventually thought I was sorted and went home. I have no signal. And I mean zilch. I’m lucky to have 1 bar of 4g and it even went to 3G at one point. I can open nothing, I couldn’t even load a web page. My home internet is poor so I was relying on my phones internet hugely. Now this option is gone!! I had said where I lived in store and was told this was great. So off I went straight back only to be told tough. I’m fighting it and going back tomorrow to speak with the manager, but does anyone have any advice? The sales person was rude and so unhelpful when I went back, even though I was very understanding when they made a balls of the transfer earlier. Even worse I traded in my old phone so I will possibly be completely phone less! Any one have any advice?