I can’t persuade Ovo that my gas meter really does exist

Energy supplier insists meter is not registered at home where customer has lived and used it for 15 years

Ovo switched customers’ accounts to a new system, whereupon my gas account disappeared from my bills. Eventually, it was discovered that my gas meter is not registered at this property, and never has been. I have lived here for 15 years and have been paying gas bills all that time.

A letter from the network operator said I’d have to pay any shortfall accumulated, which terrifies me.