These scammers are hoping to get one fish out of so many they call. First of all, how and what they can get if they reduce other people's CC interest rate? I don't think anything that is remotely tangible. Secondly, they are not such good hearted people looking out to help people they don't even know at all. Thirdly, how in the hell they can reduce someone's CC interest rate?
Conclusion: They are simply looking for stealing people's information to steal MONEY from them. Criminals...............