Wrong order, no response

I’ve emailed, called, texted and inboxed. At first I thought it was an innocent mistake when they sent me a T-shirt won’t R120 instead of the dress I’d ordered worth over R300. Their lack of feedback, has made me realize it’s not just an innocent mistake, it’s bad business practice at best and a **** at worst. Their phone number goes straight to voicemail mail and texts and emails go unanswered. I’m beyond annoyed.