Called back and if you don't use the phone they called you get dropped. It's a scam www.heycosmo.com is the website. Just incase you all wanted to know it. Now you have the info do what you want
Found this by googling the phone number: HeyCosmo is a service for friends, family, and co–workers to communicate and stay connected in real-time and making sure they got my message. Best of all, you can ask questions and get a response immediately!
If you look up HeyCosmo they haven't updated their blog since March 2, 2009. I wouldn't recommend signing up with them. It looks like it was possibly legitimate at one point, but more then likely just a scam. What is appears is a way for someone to be able to get a hold of confidential info, say for instance your debit card number.