Subpar internet speeds only outdone by even more subpar outsourced customer service agents

Three weeks ago we called to have our bill looked at, as paying for just internet service, was marked up pretty high. We have the option of Verizon home internet in our area as well, and after 12 years you'd think they would want to keep recurring auto pay customers, right? Not apparently. An outsourced customer service agent offered us a better price for being "good customers", but we didn't pay attention that our service would be degraded. A few weeks in and we notice slower performance (verified through various throughput techniques), choppy streaming, etc. Fast forward, my husband calls to address the issue, and again, yet another outsourced customer service agent says that as 12 year customers we currently do not qualify for any discounts, and that if we want our previous speed of 500MBs, we would have to pay MORE than what we were paying before. Apparently, they do not like to offer you a discount unless you rent their modem or routers (which we all know costs even MORE money every month). Who do we speak to about the bait and switch and horrible customer service? And please don't reply with a scripted "every account is unique but we offer xfinity rewards now" nonsense. Who cares about movie tickets or discounts, we just want fair prices for good service without being tricked and treated horribly.