Very disappointed with Xfinity

I have been in a customer for over 5 years and last week I paid my bill twice because the mobile app did not think that I had already paid my bill so I thought I forgot. So I inquired about getting a credit for the double payment. I was assured by an agent on the chat that I would be getting a refund 5 days go by nothing. They asked me to provide my bank statement which I did finally got a hold of someone today and they told me my request was denied. Now I know why so many people hate Xfinity they charge extremely high prices for everything and the fees are a rip off who charges $18 for a sports fee and I don't even have any sports channels. Needless to say I am very disgusted with the service I received