Yes. Email [email protected] as soon as you can and we'll ask your new provider to stop it, then let you know what they say. You can also contact your new provider directly. For energy and broadband you have 14 days to change your mind, starting the day after your contract with your new provider is made.
Water, council tax and your TV Licence work differently: you're registered with the provider for your address rather than choosing a contract, so contact them if anything needs changing.