When it gets stateside, it is then passed on to USPS (generally, unless it is oversized, then it may be passed to another stateside logistic carrier depending on the contract Asendia has). Everyone one of the shipments I received that originated Asendia were delivered by USPS in the equivalent of First Class Mail.
As far as the Payment Not Received in the tracking information, I have never seen that before. There is an 800 number you can call to "question" what that means....although I know you probably dont want to call and be on their radar.
Payment not received could mean that the sender may have made a mistake on the customs forms, and therefore a Duty may need to be paid, or the Seller paid by check or credit card and the bank refused payment and Asendia has put shipment on hold until payment received by Recipient....ANother scenario is mistakes were made on apaperwork and there is a small administrative charge that Asendia assesses to correct the problem.....and unfortunately they want the recipient to cover these costs.
If it were my package, I would call them to clear it up and if any additional costs you incur, ask the Seller to make it right....
I would love to know what you find out as it may help others on this forum if ever faced with this issue....
Good luck 5-0
any insight is appreciated