Laravel cashier (Stripe) - How to create subscription for metered usage?

I'm having some trouble trying to implement Cashier (Stripe) into my Laravel application.

What I'm trying to do is create a new subscription on an already existing customer (company). But when I do so I get the following error:

You cannot set the quantity for metered plans.

This is what I tried to do:

$company = Company::find(1);    
$company->newSubscription('prod_GTnWPCpstGje6M', 'plan_GTnaYrAIhB6jBV')->create();

In the laravel documentation I found this

$user->newSubscription('main', 'premium')->create($paymentMethod);

but as far as I understand, if the customer already exists I don't need to pass a paymentMethod in the create() method, since it pairs with the stripe_id in the database.

In case the paymentmethod was required I also tried like this:

$company = Company::find(1); 
$paymentMethod = $company->defaultPaymentMethod()->id;
$company->newSubscription('prod_GTnWPCpstGje6M', 'plan_GTnaYrAIhB6jBV')->create($paymentMethod);

But I get the same error message.

In the Stripe dashboard I found this request body in the error log:

{
  "expand": {
    "0": "latest_invoice.payment_intent"
  },
  "plan": "plan_GTnaYrAIhB6jBV",
  "quantity": "1",
  "off_session": "true"
}

So the newSubscription() apparently passes a quantity of 1 by default.

So back to my question: How do I create a new metered subscription on an existing customer without passing a quantity?

via Chebli Mohamed