I'm trying to be respectful, but I'm not sure how they could be much more clear.  This issue has caused me some sleepless nights.  In the past, I have had to contact bill.com and tell them to void the bill and check on THEIR side only and do nothing on the QBO side.  You should be able to then do a deposit in the current month to clear it out and send over a new bill to bill.com.  It is an utter fail on both sides to allow bill.com to void a check in a prior period.  Hope this helps a bit.  Best of luck.