Suberbalist did not fully refund me after an exchange

I returned 3 items. I received a refund for one of the items for R549. The two other items (for R279 and R399) have not been refunded. I sent numerous emails and was subsequently told to go to the bank because the refund has been made. My bank confirmed that the refund hasn't been made. Superbalist agents are not responding to my emails. They say they don't know why I haven't received my money because they have processed it on their side. I offered to send bank statements to no avail. I'm still waiting for my money and don't know what to do now.