Is it okay to prank call the shampoo company?

Okay so on the back of some of the shampoo and conditioner bottles it says "Lather, rinse, repeat". then at the back there is a phone number, what if I called the phone number and say "Hey, the back of your bottle says "lather, rinse, repeat" and I have an event to go to tonight, when can I stop repeating?" Lol what would they do, is this illegal?