Prompto 10 Minute Oil Change

So you pull in and the ask you if you want the standard oil change!! You say yes... it clearly states on thier wall 21.95. You get the bill and it is now 27.95 plus tax. They argue with you as if it is your fault! I raised my voice and refused topay that price..pointing to the price on the wall. Another scamming mechanic business. Do not go here!!