Don't start with BG
Some years ago, my parents were with them. The LCD display on the meter was getting hard to read, so he contacted them to see if it could be fixed - and nothing happened until ... it went blank altogether so suddenly it was an urgent meter change since they couldn't charge for gas with the display blank.
So someone called him to make an appointment to replace the meter. He was careful to point out that the fitted meter was a fairly small model, and furniture had been custom built which precluded fitting a larger unit. So the fitter turned up with a larger unit which wouldn't fit in the space available. So they made a new appointment - IIRC just a letter telling him when it was, not a conversation to set a mutually convenient time. Also IIRC, he had a hospital appoint that clashed so told them it wasn't convenient at that time and they'd need to re-schedule it.
The next letter he had was a legal letter stating that they've bring criminal charges for theft of gas by refusing to permit the meter to be changed. My dad was not the sort of person to take that, so I pity the poor customer service rep that got his call
Eventually, they did manage to turn up with a working meter that fitted in the space available - but it certainly wasn't the smooth "excuse me, there's a problem with your meter. No problem Sir, we'll get it replaced" sort of experience where left and right hands talk to each other.
And as to the (in my opinion) fraudulent "condemning" of the boiler after he'd passed away leaving just my mum in the house, and the exorbitant quote for a replacement, the less said about their "scare a granny" incentive scheme the better.