Called about my credit cards, I don't have any, and getting a lower interest rate

Just called & left no message- did not answer because did not recognize the number.

Just called, no message left.  I DO NOT answer "unknown" numbers.

called, no message. Have blocked.

They called me, said they were with card member services, working with "the bank" and can lower interest rates on visa and MasterCard. They asked for my card number, I asked to speak to a manager, they transferred me, I asked manager for their phone number, I heard a lot of non-English speaking (sounded sort of like an Arab or Indian language) then they hung up.