Why has my bill almost doubled, when I recently asked that it be lowered??

At the end of August, my bill went up by quite a lot, and this is AFTER speaking to someone regarding lowering my bill. I live alone, work most of the time, I don't need 400 mps! I told them that, they apparently lowered me to a lower plan - but now my bill is even higher? WHY???? I tried Xfinity assistant, which, by the way, is awful. Never lets me chat to a human. I'm at work and can't sit here watching for a reply. When I call on the phone, I can never get proper help it seems. They never listen and always try to get me to go with their mobile plan. I called for customer service, not a [Edited: "Language"] sales person. This company is so frustrating, every time I try to get help. If I could get any other internet where I live, I would. Because this is basically fraud. I ask to lower my bill, and now it's double what it should me. 

Can someone PLEASE help me????