If you had auction as an option, it does not ask you to 'accept' the winning bid

It sells for what it sells for (the highest winning bid, even if there was one bid)

Once there is a bid, the 'buy it now' option goes away

Managed Payments started coming in quite some time ago, you should have had notification form eBay (email etc) about it

If you are going to cancel, you need to use the reason 'problem with buyers address' or you will get a defect

In future, don't start auctions at prices you will not really accept if you only get one bid

And also read up on the the recent/latest changes if you are still on 'PayPal' time, or you will be in for more surprises you won't like

You can read any of the hundreds of threads about managed Payments already on the forum as it it has been explained and posted about