Even leaving is a nightmare. VM are awful now

I have been with VM for a long time but the renewal price was way too high. Sky offer faster broadband and much cheaper, so I decided to leave.

Spoke to someone via WhatsApp. I was advised all my services will end on 14th September (last day of my contract). I am happy with that but then I look further into it and they have messed it up.

My most recent bill was for £42. It was raised on 27th June and covered the period 17th July until 16th August.

This means my next bill due to be raised on 27th July should cover the period 17th August until 16th September. As my service is the same, this bill should be no more than my current price of £42. 

However, I got a email saying my next bill will be for £82.28. This makes no sense my final date is 14th September and my next bill covers 17th August until 16th September (so my next bill includes my last day of service).

How have they got £82.28 if my current package (due to expire on 14th September) is £42. Where have they got this price from?

Another thing I noticed is that the email I got sent had a attachment that was called a 'Service change receipt'. This shows that my new service has a phone deal which costs £28 a month. This makes not sense as I did not request a new service. I asked all my services be disconnected on the last day of my current contract (14th September).