Open an unpaid item case 4 days after sale date.
Close it 4 days later to get the fee credited back and then you are free to relist.
After the unpaid case is closed, neither member can leave feedback.
If the buyer leaves feedback before case is closed and it doesn't auto remove, call ebay to have it removed.
If you send a Mutual cancellation the buyer may not accept it and you don't get the fee back as well as not being able to open a case.