Call, no message left

I am getting nonstop phone calls from this number.  Turns out it is a Texas phone number that inmates at Rio Cosumnes Correctional Facility in Sacramento County, California use to make outgoing collect phone calls.  I keep refusing the call, and they keep calling.

This could be a scam.Check your phone bill for this number,because they can collect on it.

I think you can put a block on numbers from DOC'S

Got several calls from this number. Message says "you have a free call from ___ (insert name - sounds like some guy says 'Tess"), an inmate from Wyandotte County jail. Press "0" to accept, press 5 to deny, press 7 to block inmate calls. So I press 7 - I don't know any inmates! Then it says, please hang up and call 800-365-0036 to register to block your number.  Dumb me, I call the 800 number..... then it says press * for information about this number; I did nothing. Then it goes into this message about how you can register for $9/month to block your number..... wtf!?!?!  I hung up.  Then I've gotten three more calls from that first 713-547-1101 number.......great.