I Cannot Use My Refurbished iPhone 11 Due to iCloud Lock

Last year, I purchased a refurbished iPhone 11 from Delta Servis in Istanbul and experienced an issue with the iCloud password. I contacted Apple, and they requested the invoice. I sent them the invoice provided by Delta Servis, which includes all the necessary details, including the IMEI number, clearly showing that the device belongs to me. Despite this, Apple refuses to accept it, claiming the document is insufficient. As a result, I am currently unable to use my device. I am filing this complaint because of this issue, and I plan to report it to the prosecutor's office as well, stating that I cannot access or use my own device.