They said they were with the IRS and were sending the US Marshall's office to arrest me if I didn't pay my back taxes.
I know I don't have any back taxes. I file them every year and I properly pay if I owe and receive a check from them if I paid too much during the year.
"do not fall for their tricks" also means do not answer the phone at all when it's a number you don't recognize.
cus now they know you have a working number. and can call back using other numbers.