I had Xfinity for over 10 years...now i cancelled and you want to charge over $1000 in cancellation

We have had Xfinity for over 10 years in our business.  While a firm believer in not changing something that is working, the service provided in the last few months has been dreadful.  We would constantly lose internet, at all times of the day, disrupting our work and our remote workers that were connected to the office. Also we started noticing that our phone lines would also go down and sometimes we would not notice. Our business is international, and the internet and phones are the most basic of needs.  Xfinity called several months ago and went over some ideas to lower the sudden higher bill.  I didn't realize that they were then extending a contract with cancelation fee.  Now a few months later we were offered ATT fiber, after much consideration we decided to give it a go.  I didn't cancel Xfinity right away to see how it worked. The internet service has been amazing, we havent dropped the internet or phone once.  I now cancelled and they are trying to charge a cancelation fee.  After being a loyal customer for so long and after encountering endless phone calls to reconnect service, i do not feel i should have to pay a cancelation fee. Please let me know how to waive this.