Engagement Ring Diamonds out (Lost)

We had placed an order for our ring to be made by DIAMFIN GROUP.An order was generated by them,we made an EFT payment of R10000.00 the outstanding amount of R13290.00 was to be paid on collection which we did on the 23rd of October 2015.The ring is very beautiful ALLOY SETTING 9k (two tone)Main Diamond 0.30 Carats with (1-2pt) diamonds all in all 85 diamonds. The actual cost of the ring insurance value is R35557.00.We were very happy with our ring at first but realised on the 11th of November 2015 that one of the diamonds are lost(1-2pt) I contacted them and complained about the diamonds falling out and that it is not our problem they did the making and setting of our ring.Francina said it will cost us R750.00 to replace the diamond but that i can take the ring to AZTEC JEWELLERS accredited registered diamond dealer in Nelspruit and claim it back from our insurance.To us it is not the point more diamonds are lost and it is not what we paid for 85 diamonds the bigger the diamonds the more expensive it gets.We feel that they are passing the buck and do not want to take responsibility. what will the ring cost us in the near future if this keeps going on. this is not fair.