Pathetic service

I bought a 2017 Renault Duster in 2017 at Renault Woodmead, all my services have been done at the same Renault consistently for the last 3 years. On my last two services I told them that my gearbox jumps out when reversing and I was told that there is no problem. Now with my 90000km service I was then told that my gearbox needs to be replaced when yet I made them known of this problem way before my 90000km service. My car was then booked in almost two weeks ago and I still do not have my car back, I have left messages and no one has come back to me. The last time someone spoke to me was that the assessor still needs to evaluate the gearbox to see whether or not they are going to repair or replace my gearbox. This service is unacceptable I have not been given a courtesy car during this time and had to borrow a vehicle from a family member to assist me in going to work. My experience with Renault has been appalling and disheartening that I am so tempted to change my brand.