Bad Service, reaping peoples monies

I have enquired about the dress advertised on Whatsapp and was told only 1 size left on the different colour. I advised the seller that I dont like the colour will leave the dress but she immediately texted me telling she got it will exchange with someone and she called me to confirm.She sent me price plus courie with banking details, I immediately made a payment of which she confirmed receival.After a week I inquired when will I receive my parcel she apologized telling me it will leave on Monday now its 3 weeks after and have not received my parcel and my Whats app are no longer been rep**** to or read. I tried calling several times with no response, later she asked if she can call me later I agreed but till today no call or response