Ignore some MSN (DID Numbers) completely from zaptel

i´ve set up an freepbx-system(pbx in a flsh) with an ISDN Line but asterisk should only react on 1 of those 10 Nummbers on this digital line. I´ve configured inbound route for that number and all works well, but if i call an unconfigured number the call is answert by asterisk with something like “Number not available”. He should ignore this number completely. My seperate fax-system doesn´t get an call anymore till i set up this and freepbx graps all nummbers.

MAy someone can tell me what i have to configure?