Jet online refusing tovrefund my discount

I purchased goods at jet online in october and entered a valid discount voucher code whoever when i checked out i still ended up paying the normal price for the goods i then contacted jet online numerous times via email (15emails) from the 30th october till the 14th november and sent them screenshots of the discount voucher they then confirmed its a valid voucher then the matter was escalated to the online refunds department then i got no feedback i then contacted them again a few times and they got back to me on the 7th november to say my refund has been approved but they experiencing a system error and their IT department is working on the matter but i still did not get the refund then i emailed them again (guess what they said) on 7th november "Your Goods will be delivered mid next week" ( I actually received my goods a long time ago and did not know what they were talking about) I then told them i dont want any goods delivered next week as i have received my order long ago i want my refund then on the 11th november they emailed me to say my account has been credited and will reflect on my next statement, I then downloaded my statement on the 15 november and saw that there was no discount refunded and emailed then to say my account has not been refunded but still havent got any replies from them in the last 10 days I then went to pay my account today and checked my balance and they still did not refund me please deal with your *********** staff at jet online