Bosch MMB6172S Blender Rust Issue - Refund Delay Problem

I bought a Bosch MMB6172S smoothie blender on 26 November from Bosch store. Before using it, I washed the product. In the evening when I came home and picked it up to put it in its place, I saw that the blade part had rust on it. I immediately called the store, they were very kind and directed me to the service. The service called the same day, asked for photos and then informed me that my refund or exchange had been approved, but that I would be called by the central office. Since 27 November I have been waiting for a solution, but for about a week nobody has called me and my problem has not been resolved. I have a product that I have paid for but cannot use, so I cannot buy a new one instead, and since I bought it because I really needed it, I am clearly victimized in this process. On top of this, although I am even willing to pay the difference and get an upper model, Bosch’s quality disappointing me this way and the service process also causing victimization is really upsetting. I request that my defective Bosch MMB6172S smoothie blender, whose refund or exchange has already been approved by the service, be processed immediately and that I be allowed either to exchange it with an upper model by paying the difference or to use its full value to purchase a different product, so that this grievance is resolved without any further delay.