Changing App Store location on iPhone?

I tried to purchase an app on my iPhone but it said I'm logged in in the Belgian store and I have to switch back to the Irish store. Can anyone tell me how to do so?

The only way to change locations is by using an Irish Apple ID… If you have an old Apple ID made with location Ireland selected, use it again. If you don't, create a new Apple ID with location Ireland.
After you remembered or created the new Irish Apple ID, go to Settings then iTunes and App Stores and sign out then sign in with the new one, it will tell you that App Store will switch to Irish App Store.