Unplug all my chargers or spend the effort somewhere else on the bill Money & Paperwork

Your dad is describing a real effect at 1995 scale. A modern phone charger left in the wall with nothing attached draws something in the region of 0.1 to 0.3 watts. Twelve of those is a few watts, call it 30 kilowatt hours over a year, which is single figures in most currencies. It is not the reason your bill went up.

What is worth chasing, in rough order:

• The games console, if it's in instant-on or rest mode. Those can sit at 10 to 15 watts constantly, which dwarfs every charger in the flat combined
• The TV if it's an older one, and anything with a set top box attached
• Anything that makes heat: kettle, oven, tumble dryer, electric shower, immersion heater
• An old fridge or freezer, which runs 24 hours a day and can be double a modern one

Buy a plug-in energy monitor for the price of a takeaway. Ten minutes of moving it around will tell you more about your specific flat than any amount of general advice, mine included.

Also check whether your rate changed rather than your usage. A lot of bills that go up have nothing to do with behaviour, and it's worth comparing kilowatt hours used against the same month last year before optimising anything. If the units are the same and the money is different, unplugging chargers will not help at all.

Small nuance on chargers: an old, cheap, unbranded one from ten years ago can genuinely draw a watt or two idle, and a few of those get warm, which is the real reason I don't leave the very old ones plugged in. Modern ones are essentially asleep.

The printer you use twice a year is worth unplugging, not really for the standby draw but because some of them wake up and run a maintenance cycle on a timer. That's ink and power for a document nobody asked for.

Anything plugged in draws full power whether it's on or not, that's just how electricity works.