I answer they hang up.

Called my mobile 9:15a today, left no voicemail. Could be part of a pattern, as I've received 2 previous calls this week from numbers starting with 213-277. Both were widely reported on this site as scams (take a "survey" and get a free vacation or free cruise).

Report Them
donotcall.gov

Called my DNC home line. No message. Blocked the number.

Credit card scam.