Waupun police are warning residents about a scam involving pre-paid Visa cards. The Waupun Police Department has received several calls from citizens who say the caller says the person has won money and to claim the cash they should go to Walgreens or Radio Shack to get a Green Dot card or Money Pack card. The caller asks residents for the three digit number on the back of the card — activating it. Police say once the card is activated you have lost the money. WE Energies also posted a customer aler that scammers are threatening disconnection to convince customers to purchase pre-paid credit cards and provide the information to them.