Let me help you with that, !
Ever wonder why your photos are darker when printed, ?

Don't forget your phone screen is artificially brightening your photo. Once printed, the luminosity just won't be the same.

If you're worried that your photos will print dark, here's a few tips to make sure it doesn't happen again:

1️⃣ turn down your phone screen's brightness
2️⃣ check each photo & see if you need to adjust your photo's brightness
3️⃣ Increase your photo's brighteness before ordering your prints using your phone photo app, or any other editor.
I hope this helps!