Target Debit Card Scam

I was contacted by phone and told I was eligible for a 50% reduction in my monthly fee if I paid 6 months up front and payment was made using a Target debit card. I know this is a scam, but played along. The person I spoke to said they would pay my next month's bill. After getting off the phone with this person, I received an email from Comcast saying a payment was made. I went to my account and the Comcast records show two payments from two different checking accounts. I am sure these payments are pending and will disappear tomorrow or the next day. During our conversation the person I was speaking to knew the last four digits of my Comcast account number and the amount of my standard monthly charge. How did they know that? Is there anything I need to do as a response to their knowledge of my phone number and my account number? Thanks. Kevin