Will Kirkman of The Telegraph newspaper has published a series of articles about how to get utility company customer services listen to your complaints.  You can find them on the Telegraph website here:

British Gas: https://www.telegraph.co.uk/money/consumer-affairs/british-gas-contact-complain-customer-service-how-make-complaint/

BT: https://www.telegraph.co.uk/money/consumer-affairs/bt-contact-customer-service-how-complain-make-complaint/

E.ON: https://www.telegraph.co.uk/money/consumer-affairs/eon-contact-complain-customer-service-how-make-complaint/

EDF Energy: https://www.telegraph.co.uk/money/consumer-affairs/edf-energy-contact-complain-customer-service-how-make-complaint/

NPower: https://www.telegraph.co.uk/money/consumer-affairs/npower-contact-complain-customer-service-how-make-complaint/

Plusnet: https://www.telegraph.co.uk/money/consumer-affairs/plusnet-contact-how-complain-customer-service-complaint/

SSE: https://www.telegraph.co.uk/money/consumer-affairs/sse-contact-complain-customer-services-how-make-complaint/

Scottish Power: https://www.telegraph.co.uk/money/consumer-affairs/scottish-power-contact-complain-customer-services-how-make-complaint/

Sky: https://www.telegraph.co.uk/money/consumer-affairs/sky-contact-how-complain-customer-service-team-cancel/

TalkTalk: https://www.telegraph.co.uk/money/consumer-affairs/talk-talk-contact-customer-service-how-make-complaint-cancel/

Virgin Media: https://www.telegraph.co.uk/money/consumer-affairs/virgin-media-contact-how-complain-customer-service-make-complaint/

Vodafone: https://www.telegraph.co.uk/money/consumer-affairs/vodafone-contact-how-make-complaint-customer-services-complain/