Complete lack of any service
I purchased a product from the US and paid US$80 for expedited delivery because it was needed urgently. The seller requested my email address and gave DHL my email and delivery address. I received a notification from DHL via email subsequently saying my parcel was on its way. Then nothing...for WEEKS! The seller repeatedly contacted DHL to find out what was happening and they repeatedly said they were unable to get hold of me. At no point did they state that they had no contact details for me. 

Eventually when I was in a position to I was able to contact DHL and was informed that they had had no email or phone number for me and so my parcel was sitting at clearance waiting for me to pay import duty and was about to be sent back. This was a total lie, I have proof that DHL had my email from the first email they sent when the parcel left the US, at no point did they try and contact me again to notify me that I needed to pay duty. How they can also take a parcel from a supplier without asking for the receiver's phone number I cannot fathom...!

Basically I paid US$80 for 3-7 day delivery and I got my parcel six weeks later and that is clearly DHL's fault given they had all the information they needed to deliver the level of service they committed to.

I have tried to deal with this issue with call center representatives and get nowhere... I am owed an explanation and frankly a refund.