I am working with a customer that is having a problem with their Norstar Plus MICS system. When they dial their internal extensions like 4xxx there is no issue, or dial 717/434-4144 there is no issue; but when they connect to an IVR system and enter the digit 4 it is not recognized -- it shows on the phone display. I have checked all configurations and can find nothing that would make only the number 4 be affected.