Modern Motors review: Gearbox does not working normally

Dear sir
I am one of the owners of nissan sunny in egypt,
The car information :
Man. Year 2104
Model n17
Engine no. 716616
Chassis no. 17972
The grantee up 100000 km
My car did 39000 kilometer only
The car did the regular maintenance services on 10000 km and 15000 km.
On sunday 16th. Of april 2017
When I went to the service center in cairo (Modern motors) the agency of nissan in egypt to do the service of 40000 km. According the service schedule,
They told me there are a problem in the gearbox so they refused to change the gear oil or to fix the gearbox problem although the grantee is up to 100000 km,
The problem in the gearbox start to increase more and more, it becomes much greater than first
The nissan agency in egypt (Modern motors) refused to help, I did a complain to the egyptian authorities to do an action against the agency for the bad services,
This problem in the short time (38500 km) only that means it an industrial defect and the nissan company a big name in the world have to do according the quality rules to the customers and to change this part in the car which it is attached directly with the engine,
Please help me to solve the problem.
Kindly regards
Thank you
Ahmed abdelmoneim
+[protected]
Ahmed. [protected]@hotmail.com