"Is that how you treat customers? If you don't refund me again, I will let you know about my internet power!"

Hello.

I have had 2 buyers claim, within a week or 2 apart of each other claiming they did not receive the item. The carrier on both shipments provided photo where the item was delivered. Now normally, this would not be an unusual situation. Stuff happens, I get it. However after offering a replacement item, both customers refuse and demand a full refund. What began being suspicious about this is that both used similar wording. I still didn't think this was alarming in anyway - 2 different customers, different names, even different addresses - however each ended the conversation with "Is that how you treat customers? If you don't refund me again, I will let you know about my internet power!"

Has anyone had to deal with this before? Is this a scammer?