@Chapster.
I was poking around the registry and landed in this path (you should have this):
HKEY_CURRENT_USER\ControlPanel\PhoneCallFwd
I haven't test it all out yet but you should see a few
string value (0,1,2,3 - this may vary). As well as a
DWORD value named "
DelaySeconds". Now I have it as 30 which should indicate 30 seconds.
I've attached a screenshot below. Hopefully you can find it and modify it to your preference!