There are several reasons that prevent a message from being delivered to the recipient handset; such as the recipient mobile number is out of coverage, not in service (does not exist), closed, have technical problem or the recipient user has barred SMS delivery and all these reasons are beyond our control.
To troubleshoot your message, check your message status in Messages Reports. If your message is found in the messages report this means that Unifonic had successfully received your message. Otherwise if the message is not in your messages report this means that Unifonic did not received the message because it was rejected or there is a problem relates to the method used to send.
If your message was found in the report, refer to the message status for more details