Yes I found my own answer.....see my explanation thru this topic . Brief, Digits only works fully with other networks in Data Mode only. "Cell and Data" you can make calls but can't receive them. I'm forced to use Data Only for now.
Sorry i kept trying remove the setting and then reapplied it thru validation. And now I can receive calls on ATT SIM. I can also make outgoing call thru the DIgits App. On the iphone incoming calls are coming thru the Stock dialer.
This is nice that it works finally.