I just had the exact same experience. They follow up with a "supervisor" that gives you a confirmation number and contact number supposedly confirming your lifetime interest rate reduction. I reported it to my credit card company; hopefully, their fraud department will investigate these clowns.
I received a call from this number and stayed on the line past the message to tell them to remove my number. A non-native English speaker told me that I had no business removing my number and when I asked the name of the company, they hung up.