We have 3 lines (2 with the same number for calls and 1 for fax/broadband).
We can only call internally from one of the two lines used for calls to the fax (Extension 22) but not between the 2 lines used for calls. We get "There are no services in operation on this line" when we check diverts or *#001# to check the type of exchange.
Have we missed out something?
*UPDATE* Problem all solved! 
