Uber Charges Far More Than the Pre-Authorized Amount I Approved

On June 27th, I called a ride through the Uber app in Istanbul using my 90% discount code. The app showed a fare in the range of $2–$3 for the trip. Before the ride started, I received an authorization message from my bank for a $2 pre-authorization hold, and I approved that amount.
However, at the end of the ride, I saw that $9 had been charged to my card. While the amount I approved was $2, having a charge taken that was both far above the price range shown in the app and outside of what I authorized left me feeling seriously wronged. No additional information or warning was provided regarding the fare.
Regarding this unfair charge, I contacted Uber through the app but haven't received any response so far. I am requesting a refund of the extra amount charged beyond what I approved, along with a clear explanation as to why this discrepancy occurred.