Install charges Added back after crediting

In July I was charged $100 install fee that I was not initially made aware that I would be charged.  After two chats I finally was credited the $100.  Now on my current bill (September) I was charged a random Installation charge of $115 and also a late fee for the $115 that should not be there.  I spoke with an agent who stated this was resolved and my balance is zero.  Tonight I received an email stating my service will be shut off on 10-14 for this missing amount.  I am beyond livid being a new customer with many other options. The hoops I had to jump through to even get to an agent only to be told something was resolved when clearly it was not.  What is my escalation path because as of right now I’m thinking cancellng is the path if this is how your customer service for issues is ran.