Kia Morning 2006 P0741 Code: Torque Converter Clutch Circuit Issue and High RPM at 80km/h

Dear all, I currently own a 2006 Kia Morning and am experiencing an issue after recently having the automatic transmission serviced by a mechanic. The vehicle is now displaying Diagnostic Trouble Code (DTC) P0741: 'Torque Converter Clutch Circuit Performance or Stuck Off'. Symptoms: - The check engine light illuminates. - When driving at 80 km/h, the engine reaches approximately 2500 RPM — significantly higher than before the transmission service. Previously, at the same speed, it would only reach around 2000 RPM. I took the car to a garage where they scanned the system and confirmed the P0741 code. The issue appears related to the torque converter clutch circuit performance or being stuck in an off position. Has anyone else encountered this problem with their Kia Morning 2006? Are there known fixes or common causes for this specific fault code? Any advice or suggestions would be greatly appreciated. Thank you in advance for your help.