Over the last 10 years I've used Three a few times for a short while but their reception where I am (in London) has always been awful. However, most recently I tried their 5G home broadband. It worked pretty well but I found a much better deal with Virgin Media so I tried to cancel under their 30 day "money back guarantee" and I've never had such a headache. Their store staff repeatedly lied to my face that it didn't exist (it's still advertised on their website today) and their call-centre staff would hang up on me. Thankfully their Twitter support staff were fantastic and sorted it for me but they could only do so by raising a complaint for me. The whole thing took three months.

What a useless, broken company, AVOID. Incidentally I hear Virgin Media are similarly awful when it comes to customer service.