diff --git a/src/TinyGsmClientA7672x.h b/src/TinyGsmClientA7672x.h
index 0bc1dba..b470ac4 100644
--- a/src/TinyGsmClientA7672x.h
+++ b/src/TinyGsmClientA7672x.h
@@ -142,16 +142,16 @@ class TinyGsmA7672X : public TinyGsmModem<TinyGsmA7672X>,
         : GsmClientA7672X(modem, mux) {}
 
    public:
-    bool addCertificate(const String& certificateName, const String& cert,
+    bool addCertificate(const char* certificateName, const char* cert,
                         const uint16_t len) {
       return at->addCertificate(certificateName, cert, len);
     }
 
-    bool setCertificate(const String& certificateName) {
+    bool setCertificate(const char* certificateName) {
       return at->setCertificate(certificateName, mux);
     }
 
-    bool deleteCertificate(const String& certificateName) {
+    bool deleteCertificate(const char* certificateName) {
       return at->deleteCertificate(certificateName);
     }
 
@@ -313,16 +313,16 @@ class TinyGsmA7672X : public TinyGsmModem<TinyGsmA7672X>,
   // havetype like ".pem" or ".der".
   // The certificate like - const char ca_cert[] PROGMEM =  R"EOF(-----BEGIN...
   // len of certificate like - sizeof(ca_cert)
-  bool addCertificate(const String& certificateName, const String& cert,
+  bool addCertificate(const char* certificateName, const char* cert,
                       const uint16_t len) {
     sendAT(GF("+CCERTDOWN="), certificateName, GF(","), len);
-    if (waitResponse(GF(">")) != 1) { return 0; }
-    stream.write(cert.c_str(), len);
+    if (waitResponse(GF(">")) != 1) { return false; }
+    stream.write(cert, len);
     stream.flush();
     return waitResponse() == 1;
   }
 
-  bool deleteCertificate(const String& certificateName) {  // todo test
+  bool deleteCertificate(const char* certificateName) {  // todo test
     sendAT(GF("+CCERTDELE="), certificateName);
     return waitResponse() == 1;
   }
diff --git a/src/TinyGsmSSL.tpp b/src/TinyGsmSSL.tpp
index 045f4bc..a0f8aa4 100644
--- a/src/TinyGsmSSL.tpp
+++ b/src/TinyGsmSSL.tpp
@@ -27,8 +27,20 @@ class TinyGsmSSL {
   bool addCertificate(const char* filename) {
     return thisModem().addCertificateImpl(filename);
   }
-  bool deleteCertificate() {
-    return thisModem().deleteCertificateImpl();
+  bool addCertificate(const String& filename) {
+    return addCertificate(filename.c_str());
+  }
+  bool addCertificate(const char* certificateName, const char* cert,
+                      const uint16_t len) {
+    return thisModem().addCertificateImpl(certificateName, cert, len);
+  }
+  bool addCertificate(const String& certificateName, const String& cert,
+                      const uint16_t len) {
+    return addCertificate(certificateName.c_str(), cert.c_str(), len);
+  }
+
+  bool deleteCertificate(const char* filename) {
+    return thisModem().deleteCertificateImpl(filename);
   }
 
   bool setCertificate(const String& certificateName, const uint8_t mux = 0) {
@@ -60,7 +72,10 @@ class TinyGsmSSL {
    */
  protected:
   bool addCertificateImpl(const char* filename) TINY_GSM_ATTR_NOT_IMPLEMENTED;
-  bool deleteCertificateImpl() TINY_GSM_ATTR_NOT_IMPLEMENTED;
+  bool addCertificateImpl(const char* certificateName, const char* cert,
+                          const uint16_t len) TINY_GSM_ATTR_NOT_IMPLEMENTED;
+  bool
+  deleteCertificateImpl(const char* filename) TINY_GSM_ATTR_NOT_IMPLEMENTED;
 
   String certificates[muxCount];
 };