Hi Indiguna,
Do you also have picking list registration enabled for the item?
If so, you can click on Sales order form > Pick and Pack tab on action bar > Picking list regsitration:
On picking list registration if the status is "Activated", you can do two things: Cancel entire picking route from Header Functions button Cancel picking route
Or you can select one line from Lines section and then click on Functions > Cancel picking line
For Delivery note cancellation, again on Pick and Pack tab, look at Journals section Delivery note journal / Packing slip journal
On this journal form, you will see cancellation button
