Worst online shopping service

I purchased a power supply online it worked 3 times only, when I wanted to return on the app the return option was greyed out. I sent an email to query, there was no feedback after I received an auto reply with a ref number, when I called in again I was promised call backs, till today no feedback, and they told me that I can’t take the device to the store as I bought it online they will have to come fetch it, but don’t even have a time frame on when it might be collected