Wrong meter number could be a possibility.
I had it years ago when my gas meter was changed. I repeatedly told Southern Electric that the meter number was wrong, I kept a copy of all the meter readings, (I was having to take a photo of the meter because I couldn’t see the screen without a camera phone).
It turned out my meter number had been mixed up with one a couple of streets away. They then tried to shaft me for a £1000ish bill. I could prove my meter readings going back to about a month after it was changed, so it worked out OK in the end.
I’d be checking previous bills and meter readings, do the calculations, get them out to check the meter, if you are overpaying by £200 per month the £70 call out / check fee will be a small price to pay.
I’d also check that next door isn’t growing weed in their attic at your expense.