You can delete a customer using its ID. When a customer is deleted, all associated payment methods are also deleted, and all associated recurring billing subscriptions are canceled.

PHP 
$result = $gateway->customer()->delete('a_customer_id');

$result->success
#=> true

If the customer can't be found, you'll receive a Braintree\Exception\NotFound exception.

Arguments
customerId required, string

A string value representing an existing customer in your Vault.