Phone call

I posted yesterday about my delivery driver putting down more tip than I authorized him to. He told me he didn't bring the receipt and could enter it on his phone.

I called the store in the morning and explained what happened. They said someone would call me back. They did so and told me the GM ( general manager?) would be in today and will call me.

I am nervous about the phone call. Do I just explain to him what happened? It was only $2.50 extra but it pisses me off. I didn't want the GM to think I'm just a complainer.