Loss of income

My passenger carrier / Vito gearbox packed up. My van has been at the dealership since the 19 Dec 2022. The dealership said that they were unable to obtain spare gearbox parts as they " were out of stock " My van is a 2019. Five years old. The dealership is still waiting for one more part. The gearbox guy and myself plus my colleagues tried sourcing parts etc too. A new gearbox is 97 grand which i dont have, so I opted to have the gearbox repaired instead not knowing at the time that parts were unavailable. It didn't take long for all of us involved that parts were not available. My vehicle is part of my income and I'm trying to get Mercedes Benz South Africa to pay up. But they are stalling. I keep getting asked silly qustions. When did you give authorization to go ahead and repair the gearbox for example. I have shared all the emails between myself and the dealership yet get asked these questions when its all in the emails. I'm owed alot of money and have been very calm until today. I can't be connected to anyone else higher up that can help me. I can't not get my money and don't know what to do from here ! Besides a lawyer which I can't afford what do I do...?