Hi jude02075,
Thank you for reaching out to Apple Support Communities.
I see from your post that while you are talking on the iPhone, your face rubs against the screen and pushes buttons or hangs up on the call. I want to help. If you have a case on the iPhone, apart from the screen protector, remove it and test to see if the issue persists.
Also, is your iPhone updated? If not, make sure that you update. It’s a good idea to backup your iPhone before updating.
Here’s How to back up your iPhone, iPad, and iPod touch - Apple Support
Here’s how to: Update your iPhone, iPad, or iPod touch - Apple Support
Hope that helps.
Best Wishes!