There is Uber when I was there a year ago (seems there still is https://www.uber.com/global/en/cities/istanbul/). But on all 3 occasions that I used it, the driver tried to scam me, telling me that it didn't work and that I had to pay him outside the app. I reported the drivers but nothing was done afaik.
I had Bitaksi with a non-Turkish number, but had a problem with multiple CC's when I tried to pay. Friendly and correct driver through.
Taxis in general are a problem in Istanbul, be cautious, agree on a price beforehand or have the meeter running. Then still pay attention when paying, some switch bank notes very fast then claim that you have paid too little. Your hotel can help you.
Use Google Translate on your phone to communicate.