Xiaomi ST10 Robot Vacuum Not Working

Since I bought the Xiaomi ST10 robot vacuum three months ago, it has done nothing but let me down. The vacuum shuts off on its own while it's running, won't respond to commands, and can't even pick up dust well, even at 800 RPM, for the past month. It doesn't pick up the dust it should, but instead, it blows it around like a fan. I'm not happy with this device at all and want to send it back, but my request for a refund was turned down. Why should I have to use something that doesn't work right and doesn't do what it's supposed to do? I want my money back as soon as possible. Thank you.