I don´t have to

"I bought a similar one here last week".

Now you knew there was something fishy going on. You would have recognised them if they were here last week, and besides, the dress was too big for both of them.

"Are you sure you want this dress, and nothing else?"

"Yes" the both answered nervously.

You started walking towards the entrance. You locked the door. "I´m afraid you will have too come with me to my office." Both women were stiff with fear. As you walked into the office you asked them to sit down. You yourself stood behind them and examined their bodies with your eyes. A good catch you thought.

"I don't think you are completely honest with me. Now I want you to say what you have taken and why."