How to re-register refit handlers in MAUI

In my MAUI, I register custom auth handlers using the following code snippet.

public static class MauiProgram
{
	public static MauiApp CreateMauiApp()
	{
		var builder = MauiApp.CreateBuilder();
		builder
			.UseMauiApp<App>()
			.UseMauiCompatibility()
            .UseMauiCommunityToolkit()
			.RegisterRefitClients()
		return builder.Build();
	}
}

And my RegisterRefitClients extension method looks like this.

public static MauiAppBuilder RegisterRefitClients(this MauiAppBuilder mauiAppBuilder)
        {
            mauiAppBuilder.Services.AddRefitClient<IMyApiService>()
                            .ConfigureHttpClient(c => c.BaseAddress = new Uri(Configuration.BASE_URL))
                            .AddHttpMessageHandler<AuthHeaderHandler>();

            return mauiAppBuilder;
        }

Here, the thing is, Configuration.BASE_URL can change at run time. By default, it always points to our production server. But the testers can change it to staging/dev server at run time. I want to invoke this method at run time, in order to set custom auth handler for the newly changed staging server.
But I cannot get the MauiAppBuilder instance anywhere in the app once it is initiated.
How do I call the RegisterRefitClients at run time?

RegisterRefitClients can not be called when the program start running. .NET MAUI enables apps to be initialized from a single location. The MauiProgram class is the entry point to the application, setting up configuration and wiring up services the application will use. Once the program starts, you can not change the MauiProgram.