Letter to complain about energy mis-selling
If you're having problems about how you were sold gas or electricity and you're not getting your issue dealt with, you can put your complaint in writing and request a resolution to the problem. You can contact your old or new supplier. If you're not happy and the contract was signed 14 days ago, you can get the contract cancelled with your new supplier.
This is an example letter and may not suit your specific situation.
If you need help, contact your local Citizens Advice Bureau.