I was updating some of the numbers saved as speed-dials on Friday morning & when I tried to dial someone later that day it didn't work & I got a "DIF NOT A TA" message. Plus if I try to use a speed-dial I just get "DIF NOT AN INTERNAL TA".

Can anyone help?

I'm sure I've just accidentally changed a setting somewhere & spent half a day going through the user's manual but had no luck. Any help would be much appreciated.