SubscriptionManager subscriptionManager = (SubscriptionManager) getSystemService(Context.TELEPHONY_SUBSCRIPTION_SERVICE);
TelephonyManager telephonyManager = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
List<SubscriptionInfo> subscriptionInfos = subscriptionManager.getActiveSubscriptionInfoList();
for (SubscriptionInfo subscriptionInfo : subscriptionInfos) {
    int subId = subscriptionInfo.getSubscriptionId();
    TelephonyManager manager = telephonyManager.createForSubscriptionId(subId);
    // etc
}