I gave them a sob story about how grateful I was, and that my husband and I worked for the same company and had BOTH just been laid off. Then I crackled a shopping bag into the receiver for several seconds. Then I hung up.
WARNING--BEWARE!! These callers are B I G credit card criminals, known as the card service scammers! Under NO circumstances, give these lowlifes your credit card number, or you will regret it forever!