We have an asterisk based phone system with multiple clients connected to it.
At the moment, all the extension numbers fall in the range 100 - 9999. But, now we have an issue where a particular customer wants to come onto our service and insists on keeping their existing extension list.

Is there a way of having extensions 700 for one customer, and also the same number range to another customer. But yet having them belong to a different group?

I see there is a concept of groups in asterisk but none of them seem to provide a solution to this.