Blocking a device on a Stand Along Cisco AP

Question

Hello all I have a device that is constantly trying to use some one else' credentials to authenticate and locking that persons account on one of the stand alone AP's.  I went ahead and tried to block the MAC by using the MAC filter ACL on the AP but looks like it is still able to connect and send the authentication request.  Is there a way to completely block this device? 
Here is what I did:
conf t
access-list 700 deny xxxx.yyyy.xyz1 0000.0000.0000
dot11 association mac-list 700
end
wr mem
exit
Also when I do "show acces-list" I do show hits on the "deny" ACL.

Answer 1

Thank you yes that was one of the site I used to setup the ACL.  Weird thing is that I did not see that device trying to associate in the logs however the ACL shows denies.
Bridge address access list 700
    deny   1834.51af.a953   0000.0000.0000 (110 matches)
    permit 0000.0000.0000   ffff.ffff.ffff (12 matches)
And looking at the ACS server I see the wrong authentication requests from this particular AP and the MAC address that is being denied.