I am using flutter to send this message. The template is approved and still i am getting error.

final TwilioFlutter twilioFlutter = TwilioFlutter(
    accountSid:
        'xxxxxxxxxxxxx', // replace with Account SID
    authToken: 'xxxxxxxxxxxxxxxxx', // replace with Auth Token
    twilioNumber:
        '+xxxxxxxxxxx', // replace with Twilio Number(With country code)
  );

Future<void> sendOtp(String otp, String phoneNumber) async {
  String messageBody = "Hi, Enter 123456 to continue";
  try {
    await twilioFlutter.sendWhatsApp(
      toNumber: '+91$phoneNumber',
      messageBody: messageBody,
    );
    print('OTP sent successfully');
  } catch (e) {
    print('Failed to send OTP: $e');
  }
}

I dont have A2P DLC, is that required for whatsapp messaging?
If not what could be the issue?