No. When you’ve chosen a new deal, your new supplier will handle the switching process. They’ll contact you to let you know what date you’ll be transferred over, and they’ll contact you around the switching date to ask for a meter reading. They’ll pass this on to your old supplier so they can send you a final bill. You don’t need to contact your old supplier, as the new supplier will handle everything for you.
Of course, choosing a new electricity supplier or natural gas supplier does not mean you are replacing your utility. Your utility will still deliver whatever energy supply you choose, safely and reliably. Since your utility company depends on where you live, you don't have to worry about choosing a utility company. In general, utilities are responsible for maintaining the energy infrastructure. If you experience a power outage or see a downed power line, call your utility company. These are listed in the Utility Companies column below.