Charged vat but won't provide a vat invoice

[Bigbird1]

I've recently sold my caravan privately and had to pay the site 15% commission + vat ( for basically doing nothing )
They told me the figure due verbally 6k +vat and I had to pay it over the phone before they would change the licence to my buyers . I have now requested a vat invoice for the £7200 several times and they are completely ignoring me . I presume HMRC will never receive the £1200 vat . Is there anything I can do

[pawncob]

https://www.gov.uk/report-tax-fraud

Do you know if they're VAT registered? If so, check their VAT number.
https://www.gov.uk/check-uk-vat-number

[Bigbird1]

Yes they are vat registered so thats why I can't understand why the won't issue me a vat receipt unless they aren't going to declare it