The details of your electricity or gas supplier will be contained on your bill or annual statement if you are on a Pay As You Go Tariff.
However if you are can’t find this information or are still unsure you can contact the network operator. The network operator owns and manages the infrastructure (electricity lines and pylons, gas pipes etc) that transport electricity and gas around the network in Northern Ireland. The electricity and gas supply companies who you buy energy from pay to use this infrastructure so they can get energy to your home.
So if you are unsure who supplies your gas or electricity you can contact the following companies:
NIE on 03457 643 643 or email@example.com
If you live in the Greater Belfast or Larne areas contact Phoenix Natural Gas on 03454 55 55 55 or http://www.phoenix-natural-gas.co.uk/get-in-touch/
For all other areas where gas is available contact Firmus Energy (Distribution) Ltd on 0845 6080 088 or email firstname.lastname@example.org