Despicable lack of customer service

I received the most terrible service imaginable from Courier Guy. On 23 May they tried to deliver the wrong package to me and weirdly insisted that I take it even though it was a pair of shoes that I did not order and that was way too large for anyone in our household. Fortunately I noticed that they had switched the waybills and the original purchasers' waybill was still there so I could get them to take it back. But they never brought my order. I have emailed them and have phoned them three times - often getting cut off and not being phoned back. I was phoned back once, by bizarre and unprofessional person who was trying to convince me that I did receive my package long ago. That was about 3 weeks ago. Never heard from them again and then the tracking was closed suddenly last week, saying that the POD has been received. What on earth, Courier Guy?