Gas hob not LPG gas compliant

Very disappointed. We bought a whirlpool gas hob only to find out when we had it installed that it was not LPG gas ready but natural gas ready. The installation company advised that Hirsch must send someone to do the conversion as they should have advised us before we purchased. Hirsch will not do it without seeing our COC certificate which is ridiculous because they sold us a product that wasn't compliant in the first place. This will make me rather go to a company that is upfront from the start. Very disappointed