Overcharge/Misinformed

I've been with xfinity for over 4 years and just recently moved to a new address in December. I've been charged for two accounts and I just realized on Sunday this has been going on. Since January was the first bill at the new spot the total I was quoted for was $75.91 just for internet to be due by the 3rd of each month. Meanwhile I've also been charged for $80.91 on the 15th of each month. How could I have not noticed this? Well it seems to me that when I transferred this service to this new address I'm at, instead of transferring it, they made a new account for me. I contacted customer service through the chatting feature while speaking to a live agent and they told me I only had one account. Well, someone then called me and told me I was misinformed and I do have 2 accounts, hence the two payments....gave me a bunch of detailed instructions to do to be able to solve this and nothing. I just got charged again this morning for the $80.91. I've been overcharged for the last few months which means $80.91 x 4 is = 323.64. I'm now short that much and wondering what do I do take me off two payments and be able to get my money back. At this point I'm going to dispute it through my bank. Please help...