If you have access to Netflix through T-Mobile, you'll need to visit the carrier's website to complete the cancellation. Once you're logged into your T-Mobile account, you'll want to select "Manage add-ons" under the "I want to" section.
When you reach the Add-ons page, scroll down to the “Services” section. There will be two Netflix subscriptions that you can access through the service. Deselect the checkmark you are enrolled in.
A message will pop up telling you that you will no longer have access to your Netflix account if you delete it. Click the "Continue with Removal" button to remove payments to Netflix through T-Mobile.
Once you are done, scroll to the bottom of the page and select "Continue" to delete Netflix.
