Complaint with customer service and internet plan

I am writing about receiving an internet plan that is different than what was promised by the customer service representative. I spoke with a customer service rep on 9.24 to change my plan to a promo as suggested by a friend. I was paying $77/month for 100mbps (internet only) and there was a promo plan for $49.99/month for 200mbps (internet only). The rep transfered me to another customer service department (retention), where I spoke with Dandre. He offered to help while there was no promo plan for $49.99/month 200mbps, he could give me $49.00/month for 150mbps on contract for 12 months and then renewable month-to-month for another 12 months.. He emailed me the terms to approve to change over. The speed and month-to-month renewal did not appear in the email so I asked to get this in writing. He confirmed the plan was indeed $49.99/month at 150mbps on contract for 12 months and then up to another 12 months on a month-to-month. He said not to worry, this will be all be in the contract details. So I approved the change, only to receive an email with the plan details with a speed of 100mbps and no details about the cost/month after the 12 month contract is completed.  I called back and talked to another representative who said she was very sorry but there was no plan like the one he promised and suggested I file a formal complaint.  All in all, I have spent over 2 hours on the phone with customer service with no resolution of my internet concerns.

In addition, since my plan changed, my internet connection has been very slow: 2.3mbps download, and 1.4mbps download confirmed on the xfininty speed test. I have rebooted the modem with no improvement.

I've been a customer for over 7 years and this is unacceptable.  Comast, what can you do to remedy the situation?