Can't deliver on orders and refuse to process refunds

Ordered an item in December 2020 which they did not deliver. I chased them for 7 months before they finally admitted they wouldn't be able to deliver it. Paid for it partly in cash and partly with a voucher (I got the voucher as a refund from a previous order where they also could not deliver the product and didn't refund me in cash). Been trying to get a refund out of them since June - they refunded the cash portion but refuse to honour the voucher and either refund that or issue a new voucher. Every time I call or email, I have to talk to a new junior staff member because they seem to churn staff and they flat out refuse to put me in contact with a manager or anyone with authority to resolve the issue, despite numerous requests. Do yourself a favour, avoid this company as they are dishonest and the chances of losing money are high.