The Watt Store never refunded me my money that was returned to them

I bought a lithium battery from the Watt store in October and had them collect it as the one they sent me wS s****. Red and painted black, and not what I ordered.there were no instructions or cables or guarantees which I was assured that it would have a 10 year guarantee. Christopher said to take pictures and video and send to him. He said it was the wrong battery and that they would replace it. After a month or so I was assured that they would refund my money. After weeks of enquiring when I would receive my refund they went offline with whatsapp and now the phone is on voicemail since 22nd December after I said I would lay a charge of ***** against them if they don't refund me the money!!