I have bought an apartment from invest Realstete...

I have bought an apartment from invest Realstete Ajman before world crises in 2007 and I paid 10 present of the amount but I did not give them any checks and as their policy if you cancell they will only return 30 percent of the money you have paid so I told them to cancell they did not agree and I left them and told them I don’t need anything just cancell and no answer after 12 years now they have made case against me for the remaining money and hitch is around 560000 Dhs but I did not give them any check what to do pls answer