Have gotten several and the number shows up on caller ID, but never leaves a message.

Ha, funny I got the same call from this number earlier in the morning.

I have no prior business relationship with Kforce, but one of their agents leaves me weekly voice mail messages saying he has met with others in my company.  If he really had met with others, he wouldn't be calling me.

These are telemarketing calls.

I just got a call from this number and they did not leave a message.

If it is Kforce in LA. 424 is not a Southern Californian area code.

424 is a SoCal area-code.  It's an overlay area code for 310.