That's not even really true any more - Ofcom (who are in charge of regulating telecoms here) decided that all the companies could increase their prices by inflation plus 3.9% every April without voiding people's contracts or allowing them to cancel and without having to account for this in the headline prices in all their advertisements, so naturally everyone did and ran lots of promotions based on the bogus prices right before the increase. I think they even let some companies do this when there was nothing at all in the contracts permitting it (though that may only have allowed increasing prices by inflation). There's also apparently a newer swizz where companies advertise discounted prices but calculate the price increase based on the original, non-discounted price. The whole thing stinks of regulatory capture and oligopolies and the British media and establishment doesn't seem to care. They're more interested in attacking actually-competitive sectors like supermarkets with tiny profit margins.