fix: Modem.msisdn is not a function
diff --git a/src/osmo_gsm_tester/ofono_client.py b/src/osmo_gsm_tester/ofono_client.py
index 9839f46..7e57938 100644
--- a/src/osmo_gsm_tester/ofono_client.py
+++ b/src/osmo_gsm_tester/ofono_client.py
@@ -161,7 +161,7 @@
     def sms_send(self, to_msisdn):
         if hasattr(to_msisdn, 'msisdn'):
             to_msisdn = to_msisdn.msisdn
-        sms = Sms(self.msisdn(), to_msisdn)
+        sms = Sms(self.msisdn, to_msisdn)
         self.log('sending sms to MSISDN', to_msisdn, sms=sms)
         if not self.has_interface(I_SMS):
             raise RuntimeError('Modem cannot send SMS, interface not active: %r' % I_SMS)