robbing people

i had placed an order on 21/11/2020 and normally charged 15% more on the order. the 15% is then refunded within 7 working days. its now 3 weeks and the money has not been refunded to me. i have made many calls and no one can assist. last person wanted me to send through my bank statement so their back office can issue a release letter for my bank? that is just bull ****. i dont trust sending my financial info to just anyone. i want ALL my money back even what i paid for the order!