Laravel 12, Event Listener First array member is not a valid class name or object error

I am trying to add multiple listeners on an event in Laravel 12 which is something like this:

AppServiceProvider.php

use AppEventsFrontendOTPVerificationEvent;
use AppListenersFrontend{OTPOnMobileListener, OTPOnWhatsappListener};

class AppServiceProvider extends ServiceProvider {
    ...

    /**
     * Bootstrap any application services.
     */
    public function boot(): void {
        Event::listen(OTPVerificationEvent::class, [
            [new OTPOnMobileListener, 'handle'],
            [new OTPOnWhatsappListener, 'handle'],
        ]);

        // --- OR ---

        Event::listen(OTPVerificationEvent::class, [
            new OTPOnMobileListener,
            new OTPOnWhatsappListener,
        ]);

        // --- OR ---

        Event::listen(OTPVerificationEvent::class, [
            OTPOnMobileListener::class,
            OTPOnWhatsappListener::class,
        ]);
    }
}

Events/Frontend/OTPVerificationEvent.php

class OTPVerificationEvent {
    /**
     * Public variables
     */
    public $mobile;
    public $mobileOtp;
    public $whatsappOtp;

    /**
     * Create a new event instance.
     */
    public function __construct($mobile, $mobileOtp, $whatsappOtp) {
        $this->mobile      = $mobile;
        $this->mobileOtp   = $mobileOtp;
        $this->whatsappOtp = $whatsappOtp;
    }

    /**
     * Get the channels the event should broadcast on.
     *
     * @return array<int, IlluminateBroadcastingChannel>
     */
    public function broadcastOn(): array {
        return [
            // new PrivateChannel('channel-name'),
        ];
    }
}

Listeners/Frontend/OTPOnMobileListener.php

class OTPOnMobileListener {
    /**
     * Handle the event.
     */
    public function handle(object $event): void {
        echo "<pre>";
        print_r($event);
        echo "</pre>n";
        exit;
    }
}

Listeners/Frontend/OTPOnWhatsappListener.php

class OTPOnWhatsappListener {
    /**
     * Handle the event.
     */
    public function handle(object $event): void {
        echo "<pre>";
        print_r($event);
        echo "</pre>n";
        exit;
    }
}

I am keep getting this error:

First array member is not a valid class name or object