Hello djdc2012,
Thank you for posting to Apple Support Communities.
We understand you're not able to change the TV provider in Settings. To begin with, let's be sure that iOS is up-to-date on your iPhone. Before updating, we recommend backing up your iPhone first. These articles can be of help. When you back up, you can back up using a Mac or PC rather than iCloud if you choose.
How to back up your iPhone, iPad, and iPod touch
Update iOS on iPhone
Then, make sure you're following the steps in the article here: Sign in with your TV provider on your iPhone, iPad, or iPod touch - Apple Support
If you continue to have an issue, contact Apple Support for additional troubleshooting: Get Support
Take care.