It's a scam,but call them and have some fun! Get as much information from them, but don't give them any true information about you. Use 2101 FM 369 N, Iowa Park, TX 76367, as your address, (its the address of a prison in TX)
THE IRS WILL NEVER PHONE ANYONE- THEY ONLY SEND YOU POSTAL MAIL. If if you get a postal mail always make sure it is legal - since scammer will mail you if they get hold of your address.