Help! Traveling to Istanbul with cash !

I’ll be traveling in January to Istanbul for some medical procedures and I have the option to pay cash or card. Paying with card means an additional 15% fee which would cost me almost 2 grand and I really don’t want to do that. Of course I feel nervous about taking Thousands of dollars with me. Does anyone have any experience with this or any tips? I’m not sure if I should keep it on me at all times or check it in my bag. My clinic is the Renate clinic with Dr Yazgan and I have heard wonderful things about him from different women. They have told me the amount in euros and I’m not sure if I will need to convert the cash to euros or lira. I guess that’s a question they could answer but I’m just wondering information from people who have actually done this. If you can help, I really appreciate it!