Unfair business practice

Obtained a valuation certificate on 3 September 2020 for a 1 x pair of 18ct gold earrings set with 1/10th Kruger rand in each for R30 800,00, as a result I have been paying a monthly specified premium to my insurance company - I decided to sell and was offered R3 000,00 for the earrings which is 10% of the valuation given - aware of difference between replacement value and selling value but this is extreme & have been paying a monthly insurance premium based on the valuation certificate - The Jewellery Council has attempted to mediate but the jeweller concerned is not interested. My complaint is based on the difference between the valuation certificate and selling and payment of unnecessary insurance premiums paid