The Danger of Online Billpay

So I have all kinds of automatic payments set up through Bank of America. One of them is to a Bank of America Mastercard. It simply pays $10 a month to it. Well I have more than one Bank of America credit card. I mistakenly set up two of them for this $10 payment when only one should have. The $10 was to make sure I didn't miss a payment and get hit with a late fee. Well This was set up....16 months ago. I paid off the balance on one of them about 8 months ago and canceled the automatic payment. The other kept paying. I hadn't used to latter card in YEARS. I now have a $160 credit on an account in which I have no idea where the card is and have no intentions of ever using. So I called and closed the account and will be sent a check for $160. Kind of sad closing it....the account was one of the first I ever opened...13 years ago!