Scam call

I received a scam voicemail yesterday claiming that my 50% discount was ending and I needed to call back to discuss how to keep it.  I have received scam voicemails like this one before, but I was in a mood to mess with them, and I bit off a little more than I could chew.  I called them back, and when they gave me the script about how my bill was about to double, I said "That's ridiculous.  Just go ahead and cancel my account."  They said I had an outstanding charge for this current month, and i had to pay that in order to close the account.  I (thought) I called their bluff and told them to just run it against the card on file, specifically giving them zero information about the card itself.  Imagine my surprise when I saw that the charge on my card did go through.  Now, I later spoke with an actual Xfinity rep on a different phone call and changed my current plan (the scam, if nothing else, got me to look at what I was currently paying), and I overall, I figured "Well, I learned my lesson.  At least I don't have to worry about paying my bill at the end of this month."  However, today I did a little research, and I discovered that as part of the scam, there is a possibility that the charge may be reversed or bounce and I will end up with an overdue amount?  I'm hoping someone can talk me through this, I certainly learned my lesson about thinking I'm smarter than I am.  I just want to make sure my account remains in good standing.