Accidental upgrade selected

[#1]

I accidentally clicked on an upgrade package in my account. I wanted to see the information about the package and didn't realise when I clicked it would automatically select the upgrade, thw first I realised was when I received a confirmation email.
I phoned the helpline and was told there was no upgrade order on my account that they could see see, I contacted on twitter 2 days ago but haven't had a reply.
My account stated a change is in progress but I don't want this upgrade package, can anyone help?

[#2]

I can't see any changes either, does your account still show this? Just the pre-contract information was sent so the order wasn't confirmed, there should've been a further confirmation page after the one you got to. 

[#3]

The email I received was
'Plusnet contract summary and pre-contract information' and ther were 2 documents, one was contract summary and the other was pre contract summary.
The box showing on my account saying a change is is progress only briefly flashes up now when I log in and then disappears.
I don't want the upgrade from the fibre 300 that I'm on now to the fibre 500 to go ahead so what should I do? Surely there's a cooling off period before it starts

[#4]

Yeah the email wasn't confirmation of the order, just a summary should you go ahead. There's no actual changes in progress.