does not leave a message

Got a call from this number. Caller ID says "San Diego Zoo", but the area code is outside of San Diego County. No message left.

Been receiving this call at least two times a day. Caller ID says "San Diego Zoo". Have answered and no response. Told them to quit calling and remove my number from their call list. Didn't do any good

Receive 2 calls a day.  Don't bother to answer and, of course, no message.  Caller ID on my calls say "Los Angeles, CA".

Nov. 15, 2016, 6:11 PM, Call from 323-275-5550.  Caller ID said, "SAN DIEGO ZOO."  No message.
Nov. 16, 2016, 6:12 PM. Call from 323-275-5550.  Caller ID said, "SAN DIEGO ZOO."  No message.
First, this Area Code is in LA County, not San Diego.
Since my outgoing on message on my voice mail is a warning not to call again, which constitutes legal notice, the second and subsequent calls are billable if the caller can be correctly identified.  Anyone who talks to them, Please share!
Thanks!!