Hoover Did Not Fix Drainage Error in My Dishwasher

I bought a Hoover dishwasher, and it gave a water drainage error. However, since the authorized service centers were inadequate, they told us the problem was with the drain. We had the drain inspected and repaired, but no issue was found. The machine is still having the same problem, and every time the service team comes, they ask for ₺600. Despite all our efforts and expenses, no real solution has been provided so far. We already paid this fee before, and now they’re asking for it again even before coming.