Each destination's page offers unlimited plans priced by days, plus plans with a fixed amount of GB. When we checked the Turkey page, for instance, unlimited plans ran from 1 day to 30 days and data plans from 1 GB to 50 GB; prices move, so confirm them before buying. A note beneath the plans explains that once you've used 1 GB within the same day, unlimited plans slow to 512 kbps.
YaHala recommends installing the eSIM before you leave and switching on data the moment you land. Both your inbox and the eSIMs page of your account hold the QR code and manual setup details, and iPhones running iOS 17.4 or newer show a single-tap install button.
Source: YaHala: eSIM packages for Turkey