Hi @LahiruLi1
Not sure you're still facing the issues as you described.
Ideally, when you're creating Experience Targeting (XT) activity, the control experience is automatically assigned and can't be changes in reporting at all. The control is typically the first experience created or the one Target considers as baseline. So this shouldn't be happened.
To try with as workaround -
Duplicate the activity and reorder experiences so the correct one is first.
Pause or archive the original activity.
Relaunch the new activity with the correct control.
Please let us know how it goes.