Reference: Error Codes

Status code	HTTP code	Meaning	Status message
0002	400	The message sent was too long.	Message too long.
0003	400	None of the phone numbers were valid.	Invalid phone number format ({0}).
0004	400	Too many recipients were specified.	Too many numbers have been passed (Count: {0}).
0005	400	The specified sender name is invalid.	The name of the sender is invalid.
0006	400	The transferred message does not contain any characters.	No valid message given.
0007	400	No recipient number was transferred.	No valid recipients given.

See also Reference: Global Error Codes.