adidas Dealer Took My Open Promissory Note and Won't Return It

The Adidas dealer in Turkey at Çanakkale 17 Burda Shopping Mall advertises that you can make purchases with a promissory note without a card, guarantor, or any conditions. However, when we ask Adidas directly, they claim there is no such service. After making a purchase, the store makes you sign an open promissory note and does not return it to you. I felt tricked and unsafe, knowing that an open promissory note with my signature is now out of my control. Despite my repeated requests, the store refused to provide the signed note back to me. This situation with the Adidas dealer is entirely malicious. What does it mean to sign an open promissory note and not receive it back? These practices do not align with the standards of a corporate brand like Adidas.