On command 'AT+CLCC' SIM800C returns next
+CLCC: 1,0,2,0,0,"phone_number",129,""
and your regex
^+CLCC:\s+(\d+),(\d),(\d),(\d),([^,]),"([^,]*)",(\d+)$
doesn't match it, cause response has some information in the end of the string/ According to docs it's alphaId.
fix AT+CLCC command for SIM800L module
On command 'AT+CLCC' SIM800C returns next +CLCC: 1,0,2,0,0,"phone_number",129,"" and your regex ^+CLCC:\s+(\d+),(\d),(\d),(\d),([^,]),"([^,]*)",(\d+)$ doesn't match it, cause response has some information in the end of the string/ According to docs it's alphaId.