Caller just hummed a tune and hung up

Suspect scam. Keeps calling and leaves no message.

They called saying that the warranty on my car is about to expire. They obviously didn't get the memo that I purchased extended warranty when I bought my car initially.

Extended car warranty sales people. I have a BMW and I asked if they were BMW or were a 3rd party. They said "we are a 3rd party but BMW uses us for their extended warranties." They said if I didn't purchase it today then they couldn't offer it again. I said "Well, I am not ready to buy it today and if you can't offer it at a later date, there are plenty of 3rd party warranty people I can turn to". They hung up.