Checking CEREG for ublox LTE-M

src/TinyGsmClientUBLOX.h

@@ -444,9 +444,16 @@ public:
   }
 
   RegStatus getRegistrationStatus() {
-    sendAT(GF("+CGREG?"));
-    if (waitResponse(GF(GSM_NL "+CGREG:")) != 1) {
-      return REG_UNKNOWN;
+
+    if (isCatM) {  // Check EPS registration for LTE modules
+      sendAT(GF("+CEREG?"));
+      if (waitResponse(GF(GSM_NL "+CEREG:")) != 1) {
+        return REG_UNKNOWN;
+    }
+    else {
+      sendAT(GF("+CGREG?"));  // Check GPRS registration for others
+      if (waitResponse(GF(GSM_NL "+CGREG:")) != 1) {
+        return REG_UNKNOWN;
     }
     streamSkipUntil(','); // Skip format (0)
     int status = stream.readStringUntil('\n').toInt();