[Closed] Late Invoicing of Extra Charges

I recently shipped some stuff to Australia via Air Freight, 1st went fine, 2nd seemed OK then the 3rd was flagged as being over size and extra charges were applied and paid at the time.

Now 2 months after shipment 2 was received I have been billed for oversize charges on these. I cannot easily dispute these as the boxes are now lining the floor of my bike room. The boxes were close to the Max dimensions but I measured them as they were collected. When the arrived they had been squashed and could have been measured over.

Do I have to pay? Currently holding out mostly due to the time frame after the event and lack of an invoice at the time. When is a contract over in these terms?