If you are not able to send messages to your own number; it means your number is registered in the DND registry. If you are sending messages as promotional they can not be delivered to the DND numbers, therefore, TRAI does not allow such types of SMS to DND numbers. When you get messages from your bank, online shopping websites, restaurants etc. in that case you have agreed to their terms and conditions to receive such messages from these corporate houses. You have given them your contact information and you have agreed to their terms or services.