Bad poor service

I am a retailer ordering from USA. DPD is the courier they chose. To my disappointment they are beyond the point of delivering a good service. You can mail phone and ask no one gets back to you and sent you mails with false address ant tell you that they were there and no one home and the picture provided not even ones own house. And when you query they have 3 different answers to one query? How does that work. I tried to phone Gustaf Trieghaardt at pretoria branch watloo no luck i have spoken to Ms Jele no luck and maild S Mahbena several times and no answer what must one do to get our Parcells that we paid for