[[HTTP 400] Unable to create record: Invalid parameter: To] when trying to send a verification message using twilio

i have an issue while using twilio service for verifying phone number of the users

error: [HTTP 400] Unable to create record: Invalid parameter: To

verification controller store method

    public function store(Request $request)
    {
        if ($request->user()->hasVerifiedPhone()) {
            dd('your phone was verified already');
        }

        $data = $request->validate([
            'phone_number'  => 'required|string',
        ]);

        $phone = $data['phone_number'];

        $user_verification = auth()->user()->verification()->create([
            'user_id'   => auth()->id(),
            'phone_number'  => $phone,
        ]);

        $verification = $this->verify->startVerification($phone, $request->post('channel', 'sms'));

        if (!$verification->isValid()) {
            $user_verification->delete();

            $errors = new MessageBag();
            foreach($verification->getErrors() as $error) {
                $errors->add('verification', $error);
            }

            return response()->json([
                'error' => $errors,
            ]);
        }

        return response()->json([
            'message'   => 'Your code verificaton was sent to'. $phone,
            'status'    => true,
        ]);
    }

verification method:

    public function startVerification($phone_number, $channel)
    {
        try {
            $verification = $this->client->verify->v2->services($this->verification_sid)
                ->verifications
                ->create($phone_number, $channel);
            return new Result($verification->sid);

        } catch (TwilioException $exception) {
            return new Result(["Verification failed to start: {$exception->getMessage()}"]);
        }

    }

any help i will be appreciated

thanks in advance.