DPD do not deliver the parcel to the flat door. I ...

DPD do not deliver the parcel to the flat door. I received an email pretending that my parcel was delivered in front of my door, but there was nothing and I am still running after my parcel. No success to reach the DPD hotline. It is only an answering machine saying that my parcel was delivered !
The same happened on Tuesday with another parcel which was found outside in the street.
The service and reliability is very low !