Impossible provider

We had ordered a toner set. This worked for a couple of days in use no longer, and showed "Toner Empty".
After consultation with the customer service we got immediately a new set sent to the toner to be replaced. A cartridge was defective. The defective cartridges, and are not used spare cartridges have been returned by us as agreed again. Almost three weeks then came an invoice for the decline in cartridges, with the information that no return was made. The bookkeeping then turned out to be extremely unprofessional and talking rude and threatened with debt collection - in spite of this we deposit receipt! After long discussions, the package then dipped the supplier to actually. The new cartridges seem to be working currently, but the supplier is definitely a no-go!