DPD

I ordered a laptop because i have to start a new job on Monday. I paid extra for a specific time delivery slot. I make sure i am in because DPD have claimed i have not been home before. Then i get a message saying they couldnt deliver because nobody was home. Absolutely infuriating. I live in a small block of flats and the buzzer makes a awful piercing sound thats horribly loud so i know they didn't ring the buzzer. No calling card was left and now customer services is just a computer generated system that doesn't allow me to do anything. I NEED this laptop otherwise i cannot work. After reading reviews this is a common thing to many people. How are they allowed to do this with no reprimand? I will be invoicing DPD for every hour i loose on work because of them, not to mention the stress of there pure negligence.