Theft, and no-one to contact

"Guaranteed Delivery Date", waited whole day, had to go to another shop to get the parts, they rocked up next day, unplanned. All fine? No, dropped off 5 parcels. One box was a duplicate of the other. And then of course they never delivered another part. Refund? I clearly state what the issue is, they clearly state they understand. What do they do? They refund less than the smallest item. Timeless, illiterate, and can't do simple maths. Can't contact them, no email address, Facebook Messenger I don't get a reply on, no telephone number, so it seems I am kissing the money goodbye. This is theft. Why do I do this to myself because the exact same thing happened just over a year ago. Just pathetic.