diff --git a/features/cellular/easy_cellular/CellularConnectionFSM.cpp b/features/cellular/easy_cellular/CellularConnectionFSM.cpp
index cb5e08eea1..340a0ab474 100644
--- a/features/cellular/easy_cellular/CellularConnectionFSM.cpp
+++ b/features/cellular/easy_cellular/CellularConnectionFSM.cpp
@@ -402,6 +402,8 @@ void CellularConnectionFSM::device_ready()
         _event_status_cb((nsapi_event_t)CellularDeviceReady, 0);
     }
     _power->remove_device_ready_urc_cb(mbed::callback(this, &CellularConnectionFSM::ready_urc_cb));
+    _cellularDevice->close_power();
+    _power = NULL;
 }
 
 void CellularConnectionFSM::state_device_ready()
@@ -434,7 +436,8 @@ void CellularConnectionFSM::state_sim_pin()
             retry_state_or_fail();
             return;
         }
-
+        _cellularDevice->close_sim();
+        _sim = NULL;
         if (_plmn) {
             enter_to_state(STATE_MANUAL_REGISTERING_NETWORK);
         } else {
diff --git a/features/cellular/easy_cellular/CellularConnectionFSM.h b/features/cellular/easy_cellular/CellularConnectionFSM.h
index 78dc1f232a..b0c2bdda6b 100644
--- a/features/cellular/easy_cellular/CellularConnectionFSM.h
+++ b/features/cellular/easy_cellular/CellularConnectionFSM.h
@@ -117,7 +117,9 @@ public:
      */
     CellularDevice *get_device();
 
-    /** Get cellular sim interface
+    /** Get cellular sim interface. SIM interface is released after SIM is open and ready for use (moving from STATE_SIM_PIN to next state).
+     *  After SIM interface is closed this method will return NULL. SIM interface can be created again via CellularDevice
+     *  which you can get with the method get_device().
      *  @return sim interface, NULL on failure
      */
     CellularSIM *get_sim();
diff --git a/features/cellular/framework/AT/ATHandler.cpp b/features/cellular/framework/AT/ATHandler.cpp
index fbf01f403e..5dbc834609 100644
--- a/features/cellular/framework/AT/ATHandler.cpp
+++ b/features/cellular/framework/AT/ATHandler.cpp
@@ -72,6 +72,7 @@ ATHandler::ATHandler(FileHandle *fh, EventQueue &queue, int timeout, const char
     _fh_sigio_set(false),
     _processing(false),
     _ref_count(1),
+    _is_fh_usable(true),
     _stop_tag(NULL),
     _delimiter(DEFAULT_DELIMITER),
     _prefix_matched(false),
@@ -151,6 +152,11 @@ void ATHandler::set_file_handle(FileHandle *fh)
     _fileHandle = fh;
 }
 
+void ATHandler::set_is_filehandle_usable(bool usable)
+{
+    _is_fh_usable = usable;
+}
+
 nsapi_error_t ATHandler::set_urc_handler(const char *prefix, mbed::Callback<void()> callback)
 {
     if (find_urc_handler(prefix, callback)) {
@@ -269,6 +275,10 @@ void ATHandler::restore_at_timeout()
 
 void ATHandler::process_oob()
 {
+    if (!_is_fh_usable) {
+        tr_debug("process_oob, filehandle is not usable, return...");
+        return;
+    }
     lock();
     tr_debug("process_oob readable=%d, pos=%u, len=%u", _fileHandle->readable(), _recv_pos,  _recv_len);
     if (_fileHandle->readable() || (_recv_pos < _recv_len)) {
diff --git a/features/cellular/framework/AT/ATHandler.h b/features/cellular/framework/AT/ATHandler.h
index ad5d8a787d..93e5053598 100644
--- a/features/cellular/framework/AT/ATHandler.h
+++ b/features/cellular/framework/AT/ATHandler.h
@@ -175,6 +175,13 @@ public:
      */
     void set_file_handle(FileHandle *fh);
 
+    /** Set is file handle usable. Some situations like after going to data mode, file handle is not usable anymore.
+     *  Any items in queue are not to be processed.
+     *
+     *  @param usable true for usable filehandle
+     */
+    void set_is_filehandle_usable(bool usable);
+
 protected:
     void event();
 #ifdef AT_HANDLER_MUTEX
@@ -209,6 +216,7 @@ private:
 
     bool _processing;
     int32_t _ref_count;
+    bool _is_fh_usable;
 
     //*************************************
 public:
diff --git a/features/cellular/framework/AT/AT_CellularNetwork.cpp b/features/cellular/framework/AT/AT_CellularNetwork.cpp
index b1d17a205a..6daa79b59a 100644
--- a/features/cellular/framework/AT/AT_CellularNetwork.cpp
+++ b/features/cellular/framework/AT/AT_CellularNetwork.cpp
@@ -360,8 +360,12 @@ nsapi_error_t AT_CellularNetwork::open_data_channel()
 
     _at.resp_start("CONNECT", true);
     if (_at.get_last_error()) {
-        tr_warn("Failed to CONNECT");
+        tr_error("Failed to CONNECT");
+        return _at.get_last_error();
     }
+
+    _at.set_is_filehandle_usable(false);
+
     /* Initialize PPP
      * If blocking: mbed_ppp_init() is a blocking call, it will block until
                   connected, or timeout after 30 seconds*/
@@ -385,6 +389,7 @@ nsapi_error_t AT_CellularNetwork::disconnect()
     // will set the correct sigio and nonblocking
     _at.lock();
     _at.set_file_handle(_at.get_file_handle());
+    _at.set_is_filehandle_usable(true);
     _at.unlock();
     return err;
 #else