Some recipients not receiving SMS messages originating from -C1 devices

All messages sent from the -C1 appear to be sent without issue.

When sent to certain individuals or networks the destination number does not receive the SMS message.

Issue the following command:
AT+WSCL?

Does the command result in this response?
+WSCL: 0,0

If response is 0,0 issue the following command to set the language and encoding method when composing/sending SMS messages.

AT+WSCL=1,2

The command AT+WSCL=1,2 sets the language to English and encoding method to ASCII.

Send additional SMS messages to confirm the message is received.

Additional Notes:
The +WSCL command is saved to NVRAM memory automatically.

According to the -C1 AT command guide if command AT&F is issued to -C1 series devices the +WSCL command will be set back to value of 0,0 (which is unspecified language and unspecified encoding method.) If issuing command AT&F you will need to issue AT+WSCL command to set language and coding method.

For additional information regarding the +WSCL command please refer to your product's AT command guide.