Birkenstock refund gone wrong

Bought 3 pairs of birkenstocks during the black Friday sale in November'21 via the Birkenstock webiste using the Payflex payment method . I decided to return 2 of them and up to today, after many back and forth emails and calls, I still haven't received my money back. They insisted that they paid me back but the amount is not reflecting in my account to a point where I had to send them bank statements proofing it. It is Janaury the 17th 2022 and my refund is still not reflecting on my account statement! I don't know what to do and how else to get my R2000+ cash back.