diff --git a/src/mm-iface-modem-voice.c b/src/mm-iface-modem-voice.c
index 0bba2a34..69f53cdc 100644
--- a/src/mm-iface-modem-voice.c
+++ b/src/mm-iface-modem-voice.c
@@ -2163,8 +2163,7 @@ call_list_foreach_audio_settings (MMBaseCall         *call,
                                   InCallEventContext *ctx)
 {
     if (mm_base_call_get_state (call) != MM_CALL_STATE_TERMINATED)
-        return;
-    mm_base_call_change_audio_settings (call, ctx->audio_port, ctx->audio_format);
+        mm_base_call_change_audio_settings (call, ctx->audio_port, ctx->audio_format);
 }
 
 static void
diff --git a/src/plugins/simtech/mm-shared-simtech.c b/src/plugins/simtech/mm-shared-simtech.c
index 1e651ecb..12ce9b35 100644
--- a/src/plugins/simtech/mm-shared-simtech.c
+++ b/src/plugins/simtech/mm-shared-simtech.c
@@ -53,6 +53,7 @@ typedef struct {
     /* voice */
     MMIfaceModemVoiceInterface *iface_modem_voice_parent;
     FeatureSupport              cpcmfrm_support;
+    gboolean                    audio_16k_enabled;
     FeatureSupport              cpcmreg_support;
     FeatureSupport              clcc_urc_support;
     GRegex                     *clcc_urc_regex;
@@ -1051,8 +1052,12 @@ mm_shared_simtech_voice_setup_in_call_audio_channel_finish (MMIfaceModemVoice  *
     if (!g_task_propagate_boolean (G_TASK (res), error))
         return FALSE;
 
-    if (audio_format)
-        *audio_format = NULL;
+    if (audio_format) {
+        *audio_format = mm_call_audio_format_new ();
+        mm_call_audio_format_set_encoding   (*audio_format, "pcm");
+        mm_call_audio_format_set_resolution (*audio_format, "s16le");
+        mm_call_audio_format_set_rate       (*audio_format, priv->audio_16k_enabled ? 16000 : 8000);
+    }
 
     if (audio_port) {
         if (priv->cpcmreg_support == FEATURE_SUPPORTED)
@@ -1170,12 +1175,16 @@ cpcmfrm_set_ready (MMBaseModem  *self,
                    GAsyncResult *res,
                    GTask        *task)
 {
-    GError *error = NULL;
+    GError  *error = NULL;
+    Private *priv;
+
+    priv = get_private (MM_SHARED_SIMTECH (self));
 
     if (!mm_base_modem_at_command_finish (self, res, &error))
         g_task_return_error (task, error);
     else {
         g_task_return_boolean (task, TRUE);
+        priv->audio_16k_enabled = TRUE;
         mm_obj_dbg (self, "USB audio 16k sample rate turned on");
     }
     g_object_unref (task);