How to disable AirPlay service on playing video from iPhone
You may have unknowingly played the video on an AirPlay compatible smart TV present in your network from your iPhone. You can change the playback to your iPhone or stop it.

Open Control Centre (swipe down from top right), locate and tap on the playback controls and select iPhone instead of your TV.

Refer to this Apple Support article on using AirPlay on your iPhone.


How to AirPlay video and mirror your device's screen - AirPlay video from your iPhone, iPad, or iPod touch