I have a white upside down icon (triangle not location services) in the top right corner of my iPhone

It would be better if you can please re-post with a screenshot, in order to understand the phenomenon better. Images/pictures speak louder than words. 

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With the limited information that you have provided, It is hard to even guess the problems faced by you. 

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Please re-post with detail so that someone else can help.

I repeat my question: Might it be on your wallpaper image? If you change the wallpaper is it still there?

Here are all of the iOS icons→Status icons and symbols on your iPhone - Apple Support. I don’t see what are describing. Might it be on your wallpaper image?

What model phone is that? Might it be an indication that you can swipe down from that corner to view the Control Center?