Charged by Scam through Xfinity number?

Hi!

I canceled my account in May through the Xfinity customer service number, but it didn't go through because they did not inform me of the cancellation fee. I called the same number again in June when I got charged, and they told me they could cancel it for me and refund my June charge since I tried to cancel a month prior, I would just need to pay a 100 dollar cancellation fee. After I paid over the phone, my account was canceled, and I got the payment for June credited back on my account. However, I visited the store in person because I had another cancellation fee posted to my account for 160 dollars, and the agent in the store said they never received the payment. She said the call was from a scammer, and I would have to pay the fee again. 

My question is, how did the scammer have access to all my information and how were they able to cancel my account and put the credit for the month of June on my account? Also, why were they connected to the Xfinity customer service line? I feel that Xfinity should be willing to cover my cancelation fee since I got scammed while using the number I was referred to from your site. Please help! I am frustrated and feel like I keep throwing money in the trash through Xfinity.