This is from the hotel we stayed at last week. If one whole page is needed to describe how to make phone calls between the rooms, it is not simple in my opinion.
Is there an easier way? Even if you want to give the different houses names like Lamu, Ocean front etc, give the rooms their four digit numbers and use that as the phone number too. That way our room would have been 3603 instead of L03 – no big problem for the guest 🙂