diff --git a/app-common/src/main/java/im/angry/openeuicc/core/OmapiApduInterface.kt b/app-common/src/main/java/im/angry/openeuicc/core/OmapiApduInterface.kt
index c7fed90..0a1a0be 100644
--- a/app-common/src/main/java/im/angry/openeuicc/core/OmapiApduInterface.kt
+++ b/app-common/src/main/java/im/angry/openeuicc/core/OmapiApduInterface.kt
@@ -40,20 +40,24 @@ class OmapiApduInterface(
 
     override fun logicalChannelOpen(aid: ByteArray): Int {
         val channel = session.openLogicalChannel(aid)!!
-        val id = index.getAndAdd(1)
+        val id = index.addAndGet(1)
         channels[id] = channel
         return id
     }
 
     override fun logicalChannelClose(handle: Int) {
         val channel = channels[handle]
-        check(channel != null) { "Channel $handle does not exist" }
+        check(channel != null) {
+            "Invalid logical channel handle $handle"
+        }
         channel.close()
     }
 
     override fun transmit(handle: Int, tx: ByteArray): ByteArray {
         val channel = channels[handle]
-        check(channel != null) { "Channel $handle does not exist" }
+        check(channel != null) {
+            "Invalid logical channel handle $handle"
+        }
 
         if (runBlocking { verboseLoggingFlow.first() }) {
             Log.d(TAG, "OMAPI APDU: ${tx.encodeHex()}")
diff --git a/app-common/src/main/java/im/angry/openeuicc/core/usb/UsbApduInterface.kt b/app-common/src/main/java/im/angry/openeuicc/core/usb/UsbApduInterface.kt
index 2a01c9e..f9e764b 100644
--- a/app-common/src/main/java/im/angry/openeuicc/core/usb/UsbApduInterface.kt
+++ b/app-common/src/main/java/im/angry/openeuicc/core/usb/UsbApduInterface.kt
@@ -23,6 +23,11 @@ class UsbApduInterface(
 
     override var atr: ByteArray? = null
 
+    override val valid: Boolean
+        get() = channels.isNotEmpty()
+
+    private var channels = mutableSetOf<Int>()
+
     override fun connect() {
         ccidDescription = UsbCcidDescription.fromRawDescriptors(conn.rawDescriptors)!!
 
@@ -76,10 +81,15 @@ class UsbApduInterface(
             return -1
         }
 
+        channels.add(channelId)
+
         return channelId
     }
 
     override fun logicalChannelClose(handle: Int) {
+        check(channels.contains(handle)) {
+            "Invalid logical channel handle $handle"
+        }
         // CLOSE LOGICAL CHANNEL
         val req = manageChannelCmd(false, handle.toByte())
         val resp = transmitApduByChannel(req, handle.toByte())
@@ -87,15 +97,16 @@ class UsbApduInterface(
         if (!isSuccessResponse(resp)) {
             Log.d(TAG, "CLOSE LOGICAL CHANNEL failed: ${resp.encodeHex()}")
         }
+        channels.remove(handle)
     }
 
     override fun transmit(handle: Int, tx: ByteArray): ByteArray {
+        check(channels.contains(handle)) {
+            "Invalid logical channel handle $handle"
+        }
         return transmitApduByChannel(tx, handle.toByte())
     }
 
-    override val valid: Boolean
-        get() = atr != null
-
     private fun isSuccessResponse(resp: ByteArray): Boolean =
         resp.size >= 2 && resp[resp.size - 2] == 0x90.toByte() && resp[resp.size - 1] == 0x00.toByte()
 
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..f0b1909 100644
--- a/app/src/main/java/im/angry/openeuicc/core/TelephonyManagerApduInterface.kt
+++ b/app/src/main/java/im/angry/openeuicc/core/TelephonyManagerApduInterface.kt
@@ -18,7 +18,10 @@ class TelephonyManagerApduInterface(
         const val TAG = "TelephonyManagerApduInterface"
     }
 
-    override var valid: Boolean = false
+    override val valid: Boolean
+        get() = channels.isNotEmpty()
+
+    private var channels = mutableSetOf<Int>()
 
     override fun connect() {
         // Do nothing
@@ -32,35 +35,31 @@ class TelephonyManagerApduInterface(
         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) {
+        check(channels.contains(handle)) {
+            "Invalid logical channel handle $handle"
+        }
         tm.iccCloseLogicalChannelByPortCompat(port.card.physicalSlotIndex, port.portIndex, handle)
-        valid = false
+        channels.remove(handle)
     }
 
     override fun transmit(handle: Int, tx: ByteArray): ByteArray {
+        check(channels.contains(handle)) {
+            "Invalid logical channel handle $handle"
+        }
         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
         )
     }
+}