Complaint about Price Discrepancy

I am a new Comcast customer who chose the most basic plan that was available to me. I had confirmed my service at the address where I was moving 4 days before I moved. I picked up the materials and ended up being moved to a different unit (in the same apartment building) than the one I had originally planned. I had not set up my modem/router combo yet, so I called the sales specialist that set me up previously to ask what I needed to do. He contacted global and they said they couldn't just update my address, they had to cancel my plan, which I had not even started, and then signed me up for the same plan again. However, in the 4 days since I signed and paid the deposit for, they had increased the price by $5 a month, a 12.5% increase from the original rate. Although I tried to get the same rate that I had originally paid for, I kept getting told that I "missed the promotional period" when I had already agreed to pay the original rate. Is there anything that can be done to get me the rate I had originally signed up for? I am not sure who to complain to, so I came here. 

Furthermore, I was called by someone from Xfinity, to sell me more services, so I decided to speak with him about this pricing. When I told him about the issue, he first mentioned that I was at the old address, so I'm not sure I needed to get my address changed anyway. Then he found it only when I told him the new apartment number. I asked him about the price and he said I have the same $40 a month that I originally asked for. I told him to please send me an email for proof, which he said he would and proceeded to never send it. Today, I was billed the increased rate. So now I have been lied to by Xfinity as well. Does anyone else have experience of this, is there a best course of action to take here?