Car hire not fullfilled by Naked

I have car hire with Naked, and when I need to use it, I get told they use only Europcar as their service provider, and I have an ongoing dispute with Europcar on an incorrect bill and as a result Europcar blocked my ID. So, Now, irrespective of paying for car hire, I cannot get a car because Naked refused to use another service provider or accommodate me as a client. I am entitled to a car hire as I have been paying for it for years, my dispute with the service provided should not absolve Naked from their obligation to full fill my car hire contract. I'm disappointed with this kind of customer service. There is various other car hire companies.