I cancelled my services out of contract - new one has been created without my permission!

Hey can someone advise me on a serious issue please.

I was out of contract last month (June) and cancelled my services as I went with a different provider. I was told I would be expecting a refund on the part month.

I gave notice and was told as my payment had been taken it would mean I was owed around £27.

I received an email stating my services were cancelled and then was hit with a £70+ bill. It stated this was my final bill and to be honest I wasn't bothered as I had left.

Today I recieving an email stating my bill was ready for £29? I went into my account to check and someone has created a new contract from the 4th of June! It states it's £51pcm until December 25th 2025! 

I phoned up three times today to be told my previous contract was definitely cancelled and the call handlers refusing to accept that there's a new contract. 

I gave the contract number to be told they can see it but said they'd message cancellations. This money comes out of my account in five days? 

I then asked each advisor to put me through to someone else to be just left on hold for half an hour listening to music and then the line going dead.

I have it in black and white & confirmed that my services ended last month. I have the final bill stating it was the final bill and now I have a new contract?

I left Virgin due to the ridiculous price they were offering. They were offering £67! Suddenly someone has created a contract for £51. I'm now paying my new provider and Virgin a combined £90 and they took £70+ for my final bill only two weeks ago. 

As it's been a month before they'd played this trick, I want to know how I go about sorting it?