Runaway calls, help :-(

I have this issue where someone/thing dials a number here, and it leaves a long, like 50 minutes "message". When you listen to the voicemail, it is a fax machine.

In freepbx, I have tried to prevent this by detecting faxes on inbound routes, and then terminating the call, however, it did not help.

I also added SIP settings as follows, but did not help either:

faxdetect=yes
session-timers=originate
session-expires=1200
session-minse=300
session-refresher=uas

So, I also blacklisted the offending numbers, but more keep 'popping up'.

Any idea how I can prevent these runaway calls? It is a T46G issue? Thanks in advance.