Why is Upwork charging me VAT on its fees?

Upwork pays VAT to the Turkish tax authority on the services it provides to users resident in Turkey, and on accounts without a tax number it collects 20% VAT on freelancer service fees, Connects and membership fees. Once a valid tax number is entered, Upwork stops collecting it and the registered freelancer declares that VAT and deducts it in the same period. VAT collected before the number was entered is not refunded.