Copywriters get to have final word on how exactly something should be said in any given ad, that is until the ASA listens to it. This British Gas advert which aired in December last year has been banned for "Implying that British Gas would attend same day call-outs, even over Christmas". The phrasing that set complaints off was : "You can reach us every day. Even over Christmas.", in combo with a cute animated British Gas car pulling up to help the house owner in the ad with the broken boiler.
British gas disputed the complaint, saying that they wanted the ad to show that they deal with queries every day, even on christmas - thing is, the british gas truck doesn't show up quite as fast as the ad implies.