Android app Sim card based authentication

I have created android app, for authentication purpose I want to send SMS to self number based on SIM card inserted without entering the phone number. Please suggest me solution for that.

I have tried using SubscriptionManager and TelephonyManager to fetch the phonenumber in background but it wont work in some devices.

This will get you the phone number:

https://developers.google.com/identity/phone-number-hint/android

GetPhoneNumberHintIntentRequest request = GetPhoneNumberHintIntentRequest.builder().build();
    Identity.getSignInClient(VerificationActivity.this)
        .getPhoneNumberHintIntent(request)
        .addOnSuccessListener(new OnSuccessListener<PendingIntent>() {
            @Override
            public void onSuccess(PendingIntent pendingIntent) {
                try {
                    IntentSenderRequest intentSenderRequest = new IntentSenderRequest.Builder(pendingIntent).build();
                    phoneNumberHintLauncher.launch(intentSenderRequest);
                } catch(Exception e) {
                    Log.e(TAG, "Launching the PendingIntent failed", e);
                    throw new RuntimeException(e);
                }
            }
        })
        .addOnFailureListener(e -> {
            Log.e(TAG, "Phone Number Hint failed", e);
        });

Here's the launcher:

private final ActivityResultLauncher<IntentSenderRequest> phoneNumberHintLauncher = registerForActivityResult(
        new ActivityResultContracts.StartIntentSenderForResult(),
        result -> {
            try {
                String phoneNumber = Identity.getSignInClient(VerificationActivity.this).getPhoneNumberFromIntent(result.getData());
                
                /// do stuff
                
                
            } catch (ApiException e) {
                Log.e(TAG, e);
            }
        });

To send an SMS, you need to implement a host of things including a 3rd party paid subscription.

https://developers.google.com/identity/sms-retriever/request

Good luck!