Quote:You are spot on in your analysis. Apparently the building was shared with another business and when they left some 6 months ago the system was reprogrammed by an outside contractor and has never been quite the same.
That would make sence then - one company paid for one line, and the other company the other. They would use their lines for outgoing, and their lines would ring for incoming. The two lines would have two seperate numbers and two seperate bills. They could have still have been presented as P-P though, although if they wanted less than 10 DDI's, P-MP would have been cheaper at the time (most providers now allow you to purchase DDI's in groups of less than 10).
You currently have two completely seperate 'pairs' of lines. One with one number and one with the other. There is infact a chance that one line is P-MP and the other P-P, especially if billed seperately.
It would be best to change to P-P, and this would usually not cost. Worth a phonecall. You would then have a single main number which would ring in on lines 1, 2, 3, 4, and the DDI's would also ring in on either line.
If you dial out on line 1, 2 you should see the main number for that ISDN line. There is no programming in the config file which sends a specific number as the caller ID number (you can select which number is presented to people you call for caller display and 1471 etc).