Dont ask them to agree to cancelation.  

You sold as Pick up only. They asked you to drop off. You said no. They are now required to pick up. If they havent made reasonable arrangements to do so, and picked up the item within 4 days of sale, open an Unpaid Item case.  They then have another four days to pick up the item. If they dont, close the case in your favour and relist the item.

Dont mess around by trying to get them to agree to a cancelation - you dont owe them any favours.

Ive had two different people who wanted me to drive TWO HOURS to drop something off to them, one as recently as last week!