I answered and they hung up without saying anything.

This number called my cell phone number at 3:43pm on 4-24-2017. Since it was not in my call list and they didn't leave a message, my cell phone didn't make a sound. If your cell phone has this feature, USE IT! Telemarketers are not respecting the "Do Not Call Database" setup by the FCC. Please report all telemarketers and robo callers to the FCC if you have listed yourself on the "DO NOT CALL DATABASE". The FCC really does investigate and prosecute violators. You would be helping all of us by doing so.