The worst thing I've seen so far with online order...

The worst thing I've seen so far with online orders .....
At first everything makes a professional impression, quick offer, advice on the phone, even an offer change is quick and easy.
When the money has flowed, the disaster begins ..... Deliveries come piece by piece or, as in my case, incomplete. Suddenly nobody can be reached anymore, countless e-mails are obviously ignored and not answered. For weeks now I have had an air conditioner in the corner that is not working because parts worth 250 are missing ......... only one thing remains, to call my lawyer.

Customer number: 159796
Order number: B423012
...... it would be nice if something would move now .....