If matters still cannot be resolved you can contact the Citizens Advice Bureau (CAB). The Citizens Advice consumer service provides free and independent help and advice to small businesses on energy issues, from contract issues to making a complaint or advice if you're struggling to afford your bills.
Visit the Know Your Rights publication for more information: https://www.citizensadvice.org.uk/about-us/how-citizens-advice-works/citizens-advice-consumer-work/know-your-rights-in-the-energy-market/.
You can consult The Citizens Advice Bureau at any stage in the complaints process.
Contact the Citizens Advice consumer service on 03454 04 05 06 or visit www.citizensadvice.org.uk/energy.
The link to their consumer enquiry page: https://forms.adviceguide.org.uk/complaint_energy.aspx.