Direct debit and billing

In my last correspondence with him he has told me that my bill will revert back to £74 on my next payment but I had an email off virgin thanking me for the changes I had made on my contract and the upcoming bill will be £81 so I'm waiting to see what they charge me. I put a complaint in on the chat line a couple of weeks ago and they gave me a case number but I've heard nothing since. I've had enough of chat and phoning them it's the worst customer service I've ever had from anyone, it's making me feel ill dealing with them, why no one can't just  correct my contract is ridiculous.