Yes, if you sent a message to an invalid number, your credits will be deducted. The mobile number should comes with +6 country code (for example +60123339999). We are not responsible for any failed sent SMS caused by any telecommunication companies. However, if the SMS fails to reach any number, our system will try to resend the message up to 3 times without charging extra credits. It is recommended thay you clean up the phone database from time to time to remove any invalid or old phone numbers.