Still waiting on my refund after 3 months and many promises

I enquired on a part for my car and they assured me that they can get it. They made out an invoice and told me I have to pay them before they can order the part. I made payment on 25 May... Long story short. They tried getting a mirror for me and then in August (3 months later) they promised to refund me. It is now 20 Nov and thus far they only refunded me 50% of what I originally paid and now they blocked me on WhatsApp...