Change my tv provider

From what to what?

• TV providers that let you sign in on your iPhone, iPad, or Apple TV - Apple Support
• Apps that let you sign in with your TV provider on your iPhone, iPad, or Apple TV - Apple Support
• Sign in with your TV provider on your iPhone, iPad, or iPod touch - Apple Support
• Use your pay TV or cable provider with Apple TV - Apple Support
• Set up single sign-on with your TV provider on Apple TV - Apple Support

Changing TV providers has to be done separately. Once done, you can let your Apple devices know about that change, if the new one is among of the supported providers (see list).

The TV provider setting on Apple devices is supposed to facilitate Single Sign-on to select apps from network TV content providers (ABC, NBC, etc.). Additionally, select TV providers may offer their own app to access all their channels.

This TV provider setting has no use on third party devices with the Apple TV app. What is your model device to which your question applies? Identify your Apple TV box model - Apple Support

Normally you have to cancel the subscription or contract with your current provider. Then you search for a new one and sign the new contract.