chan_misdn: Extension can never match

i have a fully updated elastix/freepbx.
there is a isdn “fritzcard” with misdn installed.
incoming calls are written with full source and destination number into my freepbx report page, but im unable to route them somewhere.

in my system log is this:
[Feb 26 16:41:32] WARNING[2714] chan_misdn.c: Extension can never match, so disconnecting on port(1).maybe you want to add an ‘i’ extension to catch this case.
[Feb 26 16:41:33] DEBUG[2714] chan_misdn.c: misdn_hangup(mISDN/2-u4)
i have no clue what i have to do with my extensions, to do something with the caller.
i tried different ones, but none of them are working for me. :frowning:

i hope one of you can give me a direction/tip/solution to fix this.