Work in pairs, pleaes.
Do 'rock-paper-scissors'. The winner is the customer. The loser is the clerk.
I'll give you worksheets. These tables are for winners. And these pictures are for losers.
Please, pass around these handouts.

First, clerks, write down the price. And say like this, "May I help you?"
Then, customers, ask the question "How much is it?"
Next, clerks, say the price and customers write the price down in the blanks. Here we go!