If your headset is faulty, the shop has to replace it and contact its distributor. SouthWing is only the manufacturer and there is an agreement with German distributors that specifies they have to replace the faulty products.
As a native English speaker, I see nothing wrong with the text as written, except perhaps a small ambiguity: who has to replace the faulty products? Is it Southwing, the German distributors or the retail shop? Also, who is the agreement between? The shops and the distributors, or the distributors and the manufacturer?