diff --git a/examples/protocols/pppos_client/components/modem/include/esp_modem_dce_service.h b/examples/protocols/pppos_client/components/modem/include/esp_modem_dce_service.h
index 447dc8a6ae..6ed14c73bc 100644
--- a/examples/protocols/pppos_client/components/modem/include/esp_modem_dce_service.h
+++ b/examples/protocols/pppos_client/components/modem/include/esp_modem_dce_service.h
@@ -61,28 +61,6 @@ static inline void strip_cr_lf_tail(char *str, uint32_t len)
  */
 esp_err_t esp_modem_dce_handle_response_default(modem_dce_t *dce, const char *line);
 
-/**
- * @brief Handle response from AT+CSQ (Get signal quality)
- *
- * @param dce Modem DCE object
- * @param line line string
- * @return esp_err_t
- *      - ESP_OK on success
- *      - ESP_FAIL on error
- */
-esp_err_t esp_modem_dce_handle_csq(modem_dce_t *dce, const char *line);
-
-/**
- * @brief Handle response from AT+CBC (Get battery status)
- *
- * @param dce Modem DCE object
- * @param line line string
- * @return esp_err_t
- *      - ESP_OK on success
- *      - ESP_FAIL on error
- */
-esp_err_t esp_modem_dce_handle_cbc(modem_dce_t *dce, const char *line);
-
 /**
  * @brief Handle response from +++ (Set Working Mode)
  *
@@ -105,50 +83,6 @@ esp_err_t esp_modem_dce_handle_exit_data_mode(modem_dce_t *dce, const char *line
  */
 esp_err_t esp_modem_dce_handle_atd_ppp(modem_dce_t *dce, const char *line);
 
-/**
- * @brief Handle response from AT+CGMM (Get DCE module name)
- *
- * @param dce Modem DCE object
- * @param line line string
- * @return esp_err_t
- *      - ESP_OK on success
- *      - ESP_FAIL on error
- */
-esp_err_t esp_modem_dce_handle_cgmm(modem_dce_t *dce, const char *line);
-
-/**
- * @brief Handle response from AT+CGSN (Get DCE module IMEI number)
- *
- * @param dce Modem DCE object
- * @param line line string
- * @return esp_err_t
- *      - ESP_OK on success
- *      - ESP_FAIL on error
- */
-esp_err_t esp_modem_dce_handle_cgsn(modem_dce_t *dce, const char *line);
-
-/**
- * @brief Handle response from AT+CIMI (Get DCE module IMSI number)
- *
- * @param dce Modem DCE object
- * @param line line string
- * @return esp_err_t
- *      - ESP_OK on success
- *      - ESP_FAIL on error
- */
-esp_err_t esp_modem_dce_handle_cimi(modem_dce_t *dce, const char *line);
-
-/**
- * @brief Handle response from AT+COPS? (Get Operator's name)
- *
- * @param dce Modem DCE object
- * @param line line string
- * @return esp_err_t
- *      - ESP_OK on success
- *      - ESP_FAIL on error
- */
-esp_err_t esp_modem_dce_handle_cops(modem_dce_t *dce, const char *line);
-
 /**
  * @brief Syncronization
  *
diff --git a/examples/protocols/pppos_client/components/modem/src/esp_modem_dce_service.c b/examples/protocols/pppos_client/components/modem/src/esp_modem_dce_service.c
index 5753c18f36..9e9550fb2a 100644
--- a/examples/protocols/pppos_client/components/modem/src/esp_modem_dce_service.c
+++ b/examples/protocols/pppos_client/components/modem/src/esp_modem_dce_service.c
@@ -42,7 +42,11 @@ esp_err_t esp_modem_dce_handle_response_default(modem_dce_t *dce, const char *li
     return err;
 }
 
-esp_err_t esp_modem_dce_handle_csq(modem_dce_t *dce, const char *line)
+/**
+ * @brief Handle response from AT+CSQ (Get signal quality)
+ *
+ */
+static esp_err_t esp_modem_dce_handle_csq(modem_dce_t *dce, const char *line)
 {
     esp_err_t err = ESP_FAIL;
     esp_modem_dce_t *esp_dce = __containerof(dce, esp_modem_dce_t, parent);
@@ -60,7 +64,11 @@ esp_err_t esp_modem_dce_handle_csq(modem_dce_t *dce, const char *line)
     return err;
 }
 
-esp_err_t esp_modem_dce_handle_cbc(modem_dce_t *dce, const char *line)
+/**
+ * @brief Handle response from AT+CBC (Get battery status)
+ *
+ */
+static esp_err_t esp_modem_dce_handle_cbc(modem_dce_t *dce, const char *line)
 {
     esp_err_t err = ESP_FAIL;
     esp_modem_dce_t *esp_dce = __containerof(dce, esp_modem_dce_t, parent);
@@ -102,7 +110,11 @@ esp_err_t esp_modem_dce_handle_atd_ppp(modem_dce_t *dce, const char *line)
     return err;
 }
 
-esp_err_t esp_modem_dce_handle_cgmm(modem_dce_t *dce, const char *line)
+/**
+ * @brief Handle response from AT+CGMM (Get DCE module name)
+ *
+ */
+static esp_err_t esp_modem_dce_handle_cgmm(modem_dce_t *dce, const char *line)
 {
     esp_err_t err = ESP_FAIL;
     if (strstr(line, MODEM_RESULT_CODE_SUCCESS)) {
@@ -120,7 +132,11 @@ esp_err_t esp_modem_dce_handle_cgmm(modem_dce_t *dce, const char *line)
     return err;
 }
 
-esp_err_t esp_modem_dce_handle_cgsn(modem_dce_t *dce, const char *line)
+/**
+ * @brief Handle response from AT+CGSN (Get DCE module IMEI number)
+ *
+ */
+static esp_err_t esp_modem_dce_handle_cgsn(modem_dce_t *dce, const char *line)
 {
     esp_err_t err = ESP_FAIL;
     if (strstr(line, MODEM_RESULT_CODE_SUCCESS)) {
@@ -138,7 +154,11 @@ esp_err_t esp_modem_dce_handle_cgsn(modem_dce_t *dce, const char *line)
     return err;
 }
 
-esp_err_t esp_modem_dce_handle_cimi(modem_dce_t *dce, const char *line)
+/**
+ * @brief Handle response from AT+CIMI (Get DCE module IMSI number)
+ *
+ */
+static esp_err_t esp_modem_dce_handle_cimi(modem_dce_t *dce, const char *line)
 {
     esp_err_t err = ESP_FAIL;
     if (strstr(line, MODEM_RESULT_CODE_SUCCESS)) {
@@ -156,7 +176,11 @@ esp_err_t esp_modem_dce_handle_cimi(modem_dce_t *dce, const char *line)
     return err;
 }
 
-esp_err_t esp_modem_dce_handle_cops(modem_dce_t *dce, const char *line)
+/**
+ * @brief Handle response from AT+COPS? (Get Operator's name)
+ *
+ */
+static esp_err_t esp_modem_dce_handle_cops(modem_dce_t *dce, const char *line)
 {
     esp_err_t err = ESP_FAIL;
     if (strstr(line, MODEM_RESULT_CODE_SUCCESS)) {