My Vestel NFK510 Fridge Still Has Issues Despite Repeated Service

There has been a persistent malfunction in our Vestel NFK510 model refrigerator for approximately two months, and no permanent solution has been provided despite multiple service attempts. The process has unfolded as follows: Initially, we contacted Vestel's authorized service due to a warning light turning on. The service team diagnosed a mainboard failure and proceeded with a replacement. However, this did not resolve the issue. Subsequently, a software update was performed. Following this update, a frosting issue began to occur in the refrigerator. The service team then stated that a "VLS" device would be installed, and if the issue persisted, the product would be taken to the workshop. To avoid further delays, I requested that the product be taken directly to the workshop and replaced if the problem remained unresolved. My request was accepted, and the refrigerator was taken in for service. However: When the product was returned to us, it had been improperly reassembled—even the screws were missing. The courier had to request the screws from us to complete the installation. We were told that the technicians had gotten into an argument and sent the unit back without inspecting it. This is unacceptable, especially from a well-established company like Vestel. Despite all these procedures, the same malfunction continues. The service was called again, and the same operations were repeated. Now, we are being told that the unit needs to be taken to the workshop once more. During this workshop process, the temporary refrigerator provided to us is very old and inadequate. Having to empty and reload the refrigerator every time is a significant waste of time and effort. Furthermore, no service reports, transaction documents, or fault assessment forms have been provided to me throughout this entire process.