Malabar Gold & Diamonds — cheating customer by purchasing diamond

We have purchased diamond 💍 at muscat with an assurance of can be possible to replace from any where. But now we went to malabar gold payyanur they told us you should go to muscat for replacement. Also they told us that our policy changed now. If your policy changed now why should i suffer for that, i purchased as per your assurance that can be changed from any where.