2 possibilities:

1) It is possible that the number that rang had an invalid caller id or no caller id.  These calls are not registered by the call blockers.  The only way to block these calls is by turning the feature 6 ON to block all calls with no caller id. 

2) The number you saw in the caller id display as "REP" is a number you already blocked.  If you press the left scroll button, the display will show the oldest number in the incoming call list (it can store up to 100 numbers, from the oldest to the newest).  Make sure you press the right button to see the last number in the incoming call list.  

If you still need help with this, please contact us at hqtelecom.com.