It has become obvious that this problem is not going to be addressed. So, before I call Excede, does anybody know what trouble code 12.5.3 is trying to show me?
You can switch services to a competitor any time -- it's your right as a consumer.
According to this site (which is maintained by someone who posts here), that code means "No inroute groups available at successfully ranged rates." I don't know what this means, but I'm sure someone here will know.