can not delte actual dates in future

[ketanco]

I am trying to review and correct a schedule done by a contractor and he put in actual dates for some activities although they are in the future. I am trying to delete those actual dates. but i can not. i go to that cell and hit delete and nothing happens. He also put in actual durations too. so I tried deleting actual durations too but all it does is to update actual dates but i still can not delete actual dates. please help, how can i delete the actual dates for future activities? on another project schedule i did myself, i cam able to do it but not on the schedule he did.