This is neither because of your cellular service provider nor your iPhone.
Your TV may not have this feature of hooking onto a Mobile Hotspot.
Probably you are using third-party apps and a third-party device.
If you are experiencing any difficulty with third-party apps or a specific website or a product then please contact the app developer or site publisher/host or the manufacturer directly. Here is how
- To contact an App developer --> How to contact an app developer - Apple Support
- To contact a web publisher —> Scroll Down to the bottom of the web page. You will find: Contact Us, Help Center, Support, Terms of use, etc.
- To contact the Manufacturer --> Please read the manual that may have come along with the product.