Dear PV, on overflow, NEXT port is 579(BIVMS Grp) for all three groups. System takes as All call forwarded from Trunk(AT). That is why all the options, always goes to AT.

But i tried set at station group
Grp 501(Grp Busy:Off, Grp Ans:Off, All Out:Off) Overflow, Next: 579
Grp 502(Grp Busy:ON, Grp Ans:Off, All Out:Off) Overflow, Next: 579
Grp 503(Grp Busy:Off,Grp Ans:Off, All Out:ON) Overflow, Next:Virtual ext which is forwarded to 579.
This it works, but on grp 502 if no answer go back to grp 501.

If anyone got any otherway to do it, please help me.