I just moved from Vodafone to ee having been with Vodafone for 18 years. The sim only package deal was so much better than Vodafone could offer. In addition ee has WiFi calling for my phone which makes it usable in my house.
If you then throw in the indifferent attitude of their call centre I had no choice. I actually wanted to stay with Vodafone but their poor service and uncompetitive package made it impossible.
I even emailed the ceo and got back a reply from a minion full of platitudes.
It's not surprising they are losing business.