Well, it's a strange provision, clause 9, because it is a bit odd that it comes to the person running the shop. I find that “may” in that clause a bit strange, because I can't imagine, if you got a complaint like this, people not saying that you had better look into it. In other words, I don't know how much discretion in practice there actually is, but that's another point.
I don't think it's necessary in the first place, but there could be another person who looks into it. It's not my bill.