Scoin Shop Mandela Democracy Medallion *******

I purchased a Democracy Medallion in March 2014 from the Scoin Shop the Glen for R35500, i was informed this would be a good investment and would get a return on this investment, i proceeded to contact the Scoin shop this year for them to buy back the coin and they advised they are currently not buying this back and i should try to sell this privately or on Auction, i have tried many platforms to sell, to no avail, i eventually got hold of the Sandton Gold exchange and they informed me that the coin is actually only worth its value in gold and which is estimated around R10 000, this is R25500 less than what i bought it for. How can a reputable company do this to people who are not aware of the value. I hereby request the Scoin shop to buy this item back from me at the price i paid and they can hold onto it as their investment.