I can't understand why every time a shipment is in...

I can't understand why every time a shipment is involved, S.D.A begins the nightmare of tracking down the package.
They are unreliable, they cannot talk to anyone, the site is practically useless couriers insist that there was no one at home but you never find the warning and this means that they never go to their destination but limit themselves to write absent just to get paid for the ride, from now on before buying with amazon or ebay or whoever I make sure that the shipment is not made by these gentlemen and I also invite you to verify this because I really wonder how they still use them after so many complaints.
good evening