Another terrible customer service experience

Yesterday I called to get an upgrade for my Internet speed. The customer support agent told me that I would receive an upgrade to 1200 mbps and it would extend my account agreement for 24 months at the same monthly price. 

I checked today and my speed did not increase and the Xfinity app showed that I still had the same plan and speed. I called customer support again today and the agent assured me that she could fix the issue. She offered me an upgrade on my speed to 1200 mbps and said the monthly price would increase by $5.00/month. I agreed to this offer. 

My system rebooted and when the cable restarted I found I no longer had access to all the channels I previously had. 

I called support AGAIN and the agent I spoke with told me that the previous agent had decreased the number of channels I get even though she never mentioned it in our discussion. 

I requested that the 3rd agent I was on the phone with change my plan back to what it previously was with the same agreement ending date. He said he couldn't do that and that I would have to agree to extending my account agreement for another year. 

This is ridiculous, but it's what I've come to expect from Xfinity support. Every time I talk to support they screw up my account. I would like someone who knows what they are doing to contact me and rectify this situation.