Caller ID shows name of caller is "California" - This is probably an auto dialer making several calls at once and caller picks up the first answerer. The rest of us get a dead line. If you continue to wait eventually you get a disconnect. This caller has called numerous times over the last months. As others have said, if you call the number back, you get a recorded message that this is a mobile phone not in service.
They called me again today and said they were from safeguard, a company which sells walk-in bathtubs. However, they used a different number this time. The number was 925-272-4590. I asked the man if he was a telemarketer and he said "yes". Then I said I wasn't interested and hung up on him. Later on I did some research on google and found out that safeguard is a real company that sells walk-in bath tubs and thier contact number is 925-272-4590. So, obviously 323-237-4563 was a spoofed number or perhaps it was a scammer pretending to be from safeguard.