All-on-6 deposit before scan

Hi everyone. I have two quotes for All-on-6 Dental Implants in Turkey and one clinic is asking for a deposit now, before I have any scan in person. They saw my panoramic xray from my local dentist but said final plan can change after CT scan there. Is that normal? I understand they need to reserve dates and hotel, but I am scared to pay and then arrive and they say I need different treatment, higher cost, or not suitable. I asked if deposit is refundable if plan changes a lot and the answer was a bit general, like “we will help you.” I am not trying to be difficult, just trying to know what other patients did. Did you pay deposit only after video call, or after written treatment plan? Also did anyone put in writing what happens if implants cannot be placed on the first trip?