I guess all mobile phones companies can be pretty useless at one time or another.
I'm with Orange and they offer a service called Best Plan, where they look at your phone usage over a 6 month period, compare it to the tariff you're on and suggest alternatives if needed.
I was on Dolphin 35, which gave 600mins and unlimited texts, for £35pm. I've not been over 200mins for over 6 months, so was quite surprised when they suggested I was already on the correct tariff for my usage.
I logged into my account via their website, went to Best Plan and they'd somehow worked out that I should probably be using their Dolphin 45 tariff with 900mins per month!
Bemused, I phoned customer services and inquired as to why they wanted me to pay them £45pm for over 4 times the inclusive minutes I was currently using, the chap agreed with me and knocked it down to 200mins with unlimited texts for £20pm.
A week or so later, they sent me a very pretty mailshot in the post with all the details of my old plan and how they'd done careful calculations to conclude that I was already on the most suitable tariff!