diff --git a/src/charm.py b/src/charm.py
index c3ce599b..8b107e16 100755
--- a/src/charm.py
+++ b/src/charm.py
@@ -5,7 +5,6 @@
 import os
 import json
 import pwd
-import subprocess
 from charms.mongodb.v1.helpers import copy_licenses_to_unit, KEY_FILE
 from charms.operator_libs_linux.v1 import snap
 from pathlib import Path
@@ -364,12 +363,7 @@ def _generate_relation_departed_key(rel_id: int) -> str:
 
     def open_mongos_port(self) -> None:
         """Opens the mongos port for TCP connections."""
-        try:
-            logger.debug("opening tcp port")
-            subprocess.check_call(["open-port", "{}/TCP".format(Config.MONGOS_PORT)])
-        except subprocess.CalledProcessError as e:
-            logger.exception("failed opening port: %s", str(e))
-            raise
+        self.unit.open_port("tcp", Config.MONGOS_PORT)
 
     # END: helper functions
 
diff --git a/tests/unit/test_charm.py b/tests/unit/test_charm.py
index e0996059..04061e4b 100644
--- a/tests/unit/test_charm.py
+++ b/tests/unit/test_charm.py
@@ -16,7 +16,7 @@
 from ops.model import BlockedStatus, WaitingStatus
 from ops.testing import Harness
 
-from charm import MongosOperatorCharm, subprocess
+from charm import MongosOperatorCharm
 
 from .helpers import patch_network_get
 
@@ -158,21 +158,3 @@ def test_mongos_host(self):
         self.harness.charm.app_peer_data["external-connectivity"] = json.dumps(True)
         mongos_host = self.harness.charm.get_mongos_host()
         self.assertEqual(mongos_host, "1.1.1.1")
-
-    @patch("subprocess.check_call")
-    def test_set_port(self, _call):
-        """Test verifies operation of set port."""
-        self.harness.charm.open_mongos_port()
-
-        # Make sure the port is opened and the service is started
-        self.assertEqual(_call.call_args_list, [mock.call(["open-port", "27018/TCP"])])
-
-    @patch("subprocess.check_call")
-    def test_set_port_failure(self, _call):
-        """Test verifies that we raise the correct errors when we fail to open a port."""
-        _call.side_effect = subprocess.CalledProcessError(
-            cmd="open-port 27018/TCP", returncode=1
-        )
-
-        with self.assertRaises(subprocess.CalledProcessError):
-            self.harness.charm.open_mongos_port()