There are 2 entries on my iPhone 6’s Settings/Privacy/Location Services for Facebook

After uninstalling Facebook app, I checked on Location services – and one FB entry ( the one with the FB logo) was gone. The other FB entry (one without FB logo) was still there.

I checked on the General/iPhone storage and there was no FB entry.

Then I re-installed FB.

On Privacy/Location services, there is one FB entry (one without FB logo)

And on General/iPhone storage there is one FB entry (with FB logo).

I tried your suggestion and the other FB entry is gone. The other FB entry remained. After installing FB again here is the screen shot.