Your customer charges the loss to the carrier whose contract it signed, and that is you. Under Article 879 of the Turkish Commercial Code, the acts and omissions of anyone you use to perform the carriage count as your own. Under Article 888(3) the contracting carrier and the actual carrier are jointly and severally liable, so the customer may claim the whole sum from either. A refrigeration failure on the hired vehicle does not lift liability either (Article 877(1)).
If you want the cold to stay in your own hands while you hire in trucks for the peak, the equipment side of fleet flexibility is the part to read.
Where the contract obliges the carrier to protect the goods against cold or heat, the defence that they spoiled by their own nature is open only if it took every measure that fell to it in choosing, maintaining and using the equipment and followed the special instructions (Article 878(4)). Only the temperature record shows on which leg the damage arose; without one the argument stays between 'it was cold when I loaded it' and 'it was warm when it reached me'. Even when a trip is arranged by phone, put the loading time, vehicle, driver and delivery regime in writing.
