Arrogant owner

We bought a digital lock from them on the 27th of March 2024. The lock was installed at a customer of mine and lasted only a week or two. We had to drive 300km to collect the lock in order to return it. They were not willing to refund us the money and wanted to give us the same type but the customer had already installed a proper Yale lock. In the end they deducted 20% from the refund money. The reason? We took more than a month to return it. These conditions were not specified on their little till slip, so we settled for the 20% "handling fee" in the end. The owner (a lady) was very arrogant and not interested at all in keeping us as customers for future. We will not buy from them again.