New GAS meter installed without my knowledge

Hello
I am the homeowner and a new GAS meter has been installed without my knowledge
There is a date as well as an opening and closing meter reading.
I have two questions.

  1. how is this allowed without my knowledge?
    It appears the person gained entry without knowledge of homeowner.
  2. how does my gas bill work now?
    How will it be accurate?
    How do I register closing reading (old meter) and opening reading of new meter) to Bulb

If what you are saying is true I would suggest it is illegal and would contact Bulb who should have details on any meter change and who if anyone authorised it.

There’s a lot to this story that doesn’t quite add up.

Is your gas meter inside the property, or in a meter box?

Is the new meter a pre-pay or a standard credit meter?

Do you have any tenants in the property who pay the bills? (they have a right to switch suppliers and arrange a change of meters - but they should ask before a meter change and you have the right to request it’s changed back at their cost when they move out).

Is there any evidence of forced entry?