Useless and rude

I purchased at Mr Price Sport for over R 2 000 then return the items and the shop did not have enough money to refund me, so I had to take a voucher. There is a jacket I want online but I cant use my voucher online. I emailed for help no reply I called in and asked to speak to a supervisor and was cut off what more must I do to try and spend money with your company ????