REG-KNPRE;
If no entries then you can add in the 3 lines below.
If the call comes in as International then it will add the 0 before the number but also add 00 as the international prefix, if your international prefix is different then change the line.
The National puts 0 and 0 before the incoming number.
ADD-KNPRE:0&&15,ISDN,INTERNAT,0,00;
ADD-KNPRE:0&&15,ISDN,NATIONAL,0,0;
ADD-KNPRE:0&&15,ISDN,SUBSCR,0,;