Unexplained June bill increase and live-chat failure — written help requested

My internet bill increased substantially in June despite no account, plan, or service changes that I made or authorized. The live-agent chat also repeatedly fails with “Unable to start a live chat session.”

Please provide a written explanation for the increase, the applicable notice or terms, and review whether a credit and comparable promotional rate are available. I want to resolve this in writing only, not by phone. I can provide account details through the appropriate private channel.