They must have had damage of some kind at the switch- maybe in the software? I worked cust svc for a cell co a looong time ago and we had that problem after we changed to a new switch. I know it's a translation problem, but I am not quite sure what causes it. (I wasn't a tech- just the poor woman people YELLED at!)
I've stopped doing that, and am honestly sorry about hollering that day...
g'night all
Heh heh,,what is your number so I can call? Just kidding.