Hi OBT,
Their numbering plan is with 1XX and 2XX.I suppose that outside callers dial similar numbers.The option that you offer with groups is quite clever solution.It would solve the problem because they use about 90 extensions.The remaining 110 numbers from their range will gather in ICD groups.Annoying is that I already use 9 and will remain less free.It turns out that the pbx simply allow dialing only existing numbers by default and it can not be changed.I accept this as a disadvantage of all TDA, TDE and NCP.

Thank you for reply