Mondo cannot make good for their mistakes

Mondo phoned me to sell a product and then delivered the incorrect product. Then they wanted to make me wait for weeks to investigate their problem before they will collect it and deliver the correct product. On top of it they keeping my admin fee but they are the ones who made the mistake. It is now months and I phone them on a regular basis that they still haven't collected the incorrect product. They keep promising that same day I phoned them that they will come back to me and I'm still waiting. I have spoken to so many employees and all they do is apologize but don't action. It has now cost me so much money because I have to keep phoning them reminding them that they still haven't collect the incorrect product they delivered, but yet still they will keep the admin fee and make me pay more money to try and get them to do their job. When I ask them what is going to happen if this product gets lost are they then going to hold me responsible and they just ignore my question. All I want is for Mondo is to come and collect the product they delivered incorrectly so that I can stop worrying about it and stop spending money on Mondo because they cannot do their work.