diff --git a/app/src/main/java/im/angry/openeuicc/core/TelephonyManagerApduInterface.kt b/app/src/main/java/im/angry/openeuicc/core/TelephonyManagerApduInterface.kt
index b7a9482..2d36277 100644
--- a/app/src/main/java/im/angry/openeuicc/core/TelephonyManagerApduInterface.kt
+++ b/app/src/main/java/im/angry/openeuicc/core/TelephonyManagerApduInterface.kt
@@ -18,49 +18,38 @@ class TelephonyManagerApduInterface(
         const val TAG = "TelephonyManagerApduInterface"
     }
 
-    override var valid: Boolean = false
+    override val valid: Boolean
+        get() = channels.isNotEmpty()
 
-    override fun connect() {
-        // Do nothing
-    }
+    private var channels = mutableSetOf<Int>()
 
-    override fun disconnect() {
-        // Do nothing
-    }
+    // Do nothing
+    override fun connect() {}
+    override fun disconnect() {}
 
     override fun logicalChannelOpen(aid: ByteArray): Int {
         val hex = aid.encodeHex()
         val channel = tm.iccOpenLogicalChannelByPortCompat(port.card.physicalSlotIndex, port.portIndex, hex, 0)
         if (channel.status != IccOpenLogicalChannelResponse.STATUS_NO_ERROR || channel.channel == IccOpenLogicalChannelResponse.INVALID_CHANNEL) {
-            throw IllegalArgumentException("Cannot open logical channel $hex via TelephonManager on slot ${port.card.physicalSlotIndex} port ${port.portIndex}")
+            throw IllegalArgumentException("Cannot open logical channel $hex via TelephonyManager on slot ${port.card.physicalSlotIndex} port ${port.portIndex}")
         }
-        valid = true
+        channels.add(channel.channel)
         return channel.channel
     }
 
     override fun logicalChannelClose(handle: Int) {
         tm.iccCloseLogicalChannelByPortCompat(port.card.physicalSlotIndex, port.portIndex, handle)
-        valid = false
+        channels.remove(handle)
     }
 
     override fun transmit(handle: Int, tx: ByteArray): ByteArray {
         if (runBlocking { verboseLoggingFlow.first() }) {
             Log.d(TAG, "TelephonyManager APDU: ${tx.encodeHex()}")
         }
-
-        val cla = tx[0].toUByte().toInt()
-        val ins = tx[1].toUByte().toInt()
-        val p1 = tx[2].toUByte().toInt()
-        val p2 = tx[3].toUByte().toInt()
-        val p3 = tx[4].toUByte().toInt()
-        val p4 = tx.drop(5).toByteArray().encodeHex()
-
-        // @formatter:off
         val result = tm.iccTransmitApduLogicalChannelByPortCompat(
             port.card.physicalSlotIndex, port.portIndex, handle,
-            cla, ins, p1, p2, p3, p4
+            tx,
         )
-        // @formatter:on
         if (runBlocking { verboseLoggingFlow.first() })
             Log.d(TAG, "TelephonyManager APDU response: $result")
         return result?.decodeHex() ?: byteArrayOf()
diff --git a/app/src/main/java/im/angry/openeuicc/util/PrivilegedTelephonyCompat.kt b/app/src/main/java/im/angry/openeuicc/util/PrivilegedTelephonyCompat.kt
index dbd39f2..a9df18e 100644
--- a/app/src/main/java/im/angry/openeuicc/util/PrivilegedTelephonyCompat.kt
+++ b/app/src/main/java/im/angry/openeuicc/util/PrivilegedTelephonyCompat.kt
@@ -111,15 +111,26 @@ fun TelephonyManager.iccCloseLogicalChannelByPortCompat(
     }
 
 fun TelephonyManager.iccTransmitApduLogicalChannelByPortCompat(
-    slotIndex: Int, portIndex: Int, channel: Int,
-    cla: Int, inst: Int, p1: Int, p2: Int, p3: Int, data: String?
-): String? =
-    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+    slotIndex: Int,
+    portIndex: Int,
+    channel: Int,
+    tx: ByteArray
+): String? {
+    val cla = tx[0].toUByte().toInt()
+    val ins = tx[1].toUByte().toInt()
+    val p1 = tx[2].toUByte().toInt()
+    val p2 = tx[3].toUByte().toInt()
+    val p3 = tx[4].toUByte().toInt()
+    val p4 = tx.drop(5).toByteArray().encodeHex()
+    return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
         iccTransmitApduLogicalChannelByPort(
-            slotIndex, portIndex, channel, cla, inst, p1, p2, p3, data
+            slotIndex, portIndex, channel,
+            cla, ins, p1, p2, p3, p4
         )
     } else {
         iccTransmitApduLogicalChannelBySlot(
-            slotIndex, channel, cla, inst, p1, p2, p3, data
+            slotIndex, channel,
+            cla, ins, p1, p2, p3, p4
         )
     }
+}