Unfortunately, it's a fairly commom scenario - a hobbyist knocking out counterfeits on new machines, because there's no way they can compete in price with the manufacturers.
That's the reason I gave up building machines - The ones in the shops got so powerful and so cheap, that there was no way to offer a resonable machine at a decent price.
You should demand a refund from the vendor - especially if you have an itemised receipt. If they are doing this 'professionally' then threaten them with a visit from the fraud police, the VAT man, the Police, and Trading Standards. That sort of approach has wonderful effects most of the time
Do NOT accept the offer of a new install, as the chances are it will simply be a variant on the theme of counterfeits.
All can say is, Good Luck!