Strange problem, customer has an FXII Expansion (17E) with a PRI. System has been in place a couple years. Couple of weeks ago the customer says there are two numbers when called from a particular phone the call will be dropped. They can go to another phone and the calls to the same numbers will complete. Checked the obvious things; changed phones, checked COS, toll restriction and all OK. After more troubleshooting I found that by removing the entry in "outbound calling number ID" under station programming the call would then complete. I found that any phone that had an entry in this field would drop calls to these numbers. When I say dropped call, the dialed number showed in the display on the phone, the next step would be ring back tone but the display would revert to normal and the call was gone. I left the "outbound calling number ID" field blank and this person has had no more problems. Today, same customer, different phone. Calls a number, gets the AA for that company, is given 6 options (Digits 1 -6) but will drop the call if digit 3 is dialed. Any other digit and the call is transferred. Remove the entry in the "outbound calling number ID" field and when the digit 3 is pressed the call is transferred. Also found by changing "Calling Number ID Mode" (PRI Board Programming) to "Default Number" (was Station Number) I can eliminate the problem. OK, so the question is why does changing these parameters allow these calls to be completed? As far as I know these parameters haven't changed since installation and now these problems arise. Any ideas?