I seem to have downloaded an app for You Tube on to my phone, and I have been on it a few times. However I am not sure if it is costing me very much and if so how do I get rid of it please.
You tube doesn't cost you a penny, unless you exceed your data allowance.
Leave it installed and only use it when you are using your own wifi at home, or when you are out and about using free wifi at a hot spot.