Online order cancelled six weeks ago - no refund granted despite numerous requests

I placed 3 online orders via the Incredible Connection website during March 2020. They were all placed on the same day.

A few days later, I was contacted by a gentleman named Jason Carelse from Incredible Connection saying the orders could not be honored due to a pricing error and I will be issued with a refund.

It's been 6 weeks since my orders were cancelled and I have received refunds for 2 of these orders only, and they were received about 3 weeks ago. The refund for one order is still outstanding.

I have emailed Jason numerous times with no response. I have chatted to Incredible Connection's online support team but they couldn't help me. I have tweeted Incredible Connection on two occasions about this with no response. I even sent them a message via Instagram to their official account with no response.

I'm not sure what else to do here to get my money back.