Nissan garage

I have two cars which I bought from Nissan company: Nissan NP 200 and Nissan Extry 2018 .I bought the cars cash and i was still working at Sasol and now I am a pensioner. Yesterday i took my Nissan Extry for backpack and cooling fan balt repair.Now i am on pension from 10.2017 and the company is still charging me the same amount. All my pension today. Please help.