Grundig VCP 5131 Sent for Repair Four Times in One Year and Still Not Fixed

My Grundig upright vacuum has been taken to the Çiğli service center for the fourth time since September 13th due to it not working. Each time, it was returned with claims that it had been repaired. However, when I used it on the same day, the same issue occurred within 5 minutes, and I called the service. They took it back on the same day, and this routine has been repeated 4 times. It is still under repair. I purchased this vacuum less than a year ago, and it is still under warranty. Given the continuous back-and-forth repairs, I no longer trust that it will work properly, and I requested a replacement. The service informed me that they reported the need for a replacement to the Aegean Regional Office, but the request was denied. They now plan to request new parts and attempt another repair. Do you not trust the word of your authorized service centers? A vacuum that hasn't even been in use for a year is returned as "repaired" only to break down the same day, and this has happened 4 times. I sent a video of the malfunction to your service team via WhatsApp. I request that all phone records be reviewed, that your headquarters provide an explanation, and that my vacuum be replaced. I refuse to accept a vacuum that has been unsuccessfully repaired multiple times.