diff --git a/README.md b/README.md
index 151b295..2acc814 100644
--- a/README.md
+++ b/README.md
@@ -33,7 +33,7 @@
 ```py
 import qpay import QPayClient
 
-client = QPayClient(host="https://merchant.qpay.mn/v2/", username="MERCHANT_USERNAME", password="MERCHANT_PASSWORD")
+client = QPayClient.instance(host="https://merchant.qpay.mn/v2/", username="MERCHANT_USERNAME", password="MERCHANT_PASSWORD")
 
 ...
 ```
diff --git a/qpay/singleton.py b/qpay/singleton.py
index 0c8038e..01de18f 100644
--- a/qpay/singleton.py
+++ b/qpay/singleton.py
@@ -6,9 +6,9 @@ class Singleton:
     __singleton_lock = threading.Lock()
 
     @classmethod
-    def instance(cls):
+    def instance(cls, *args, **kwargs):
         if not cls.__singleton_instance:
             with cls.__singleton_lock:
                 if not cls.__singleton_instance:
-                    cls.__singleton_instance = cls()
+                    cls.__singleton_instance = cls(*args, **kwargs)
         return cls.__singleton_instance