“Super slow” internet connection!!!!!!!

We started with 500GB fast internet connection when we moved to our new place. Then on time, I called Xfinity and spoke to their live agent to complained about our very slow internet connection. The person I talked said that I needed to upgrade to their “Super fast” service which will provide us 800GB of Super fast internet. However, I just have to pay extra 15/month to get the service. He also mentioned that I can I can try it and see the difference and can simply go back to my old service which is $15 less if I don’t like it. He also said that it is money back guaranteed. So I tried for couple of weeks and I didn’t see any difference. And in fact, our internet connection got worst. We only use 1 smart TV at a time and 2 cellular phones although we have smart doorbell and washer and dryer. I’m thinking that their “super fast” connection will connection will cover it but it did not. I can’t even watch Netflix properly and play reels on my phone. Our super fast turns to super slow connection. I called their live agent and I told them our problem, he said that I needed to call Netgear because I’m using their router. I called Netgear and they’ve said everything is working fine on our router. I called Xfinity again and told them that and I asked if I will just get the same worst internet connection, I would just go back to my old service and get my money back guaranteed. Unfortunately, the live agent told me that it’s no longer possible because my old promotion for my old services is no longer available and I have to pay the same amount which is $15 more to get my old services which is 500GB data. I was so frustrated and angry to the situation. I also asked them to send a technician and check our internet but live agent told me that I need to pay for that technician I want that option. I just wanted to switch with other provider. I’m not very happy with Xfinity. For the record, I am suffering with the same very slow internet connection with my unlimited data plan in my phone.