I've been with o2 for over 2 years now on the same tariff. About a year ago they offered me different deal which at the time seemed good, so I gave them the ok to change my tariff. A year later they still haven't changed it! Okay, in the end, it did kind of suite me as I decided that I prefer my current tariff anyway. But still...
Their CS has not got the best reputation.
I'm due another upgrade now, and I plan on changing my tariff too. I just hope it goes through without a hitch.