diff --git a/README.md b/README.md
index eed0107..d3ebc64 100755
--- a/README.md
+++ b/README.md
@@ -34,9 +34,9 @@ You can specify which environment when initializing `YouCanPay` instance
 
 ```php
 use YouCan\Pay\YouCanPay;
- 
-$youCanPay = YouCanPay::instance()->useKeys('my-private-key', 'my-public-key');
 
 // enable sandbox mode
 YouCanPay::setIsSandboxMode(true);
+ 
+$youCanPay = YouCanPay::instance()->useKeys('my-private-key', 'my-public-key');
 ```
diff --git a/src/API/HTTPAdapter/CurlHTTPAdapter.php b/src/API/HTTPAdapter/CurlHTTPAdapter.php
index fb09ad8..0a80f32 100644
--- a/src/API/HTTPAdapter/CurlHTTPAdapter.php
+++ b/src/API/HTTPAdapter/CurlHTTPAdapter.php
@@ -35,7 +35,7 @@ protected function parseHeaders($headers)
 
     public function request(string $method, string $endpoint, array $params = [], array $headers = []): Response
     {
-        $curl = curl_init(sprintf($this->getBaseUrl(), $endpoint));
+        $curl = curl_init(sprintf('%s%s', $this->getBaseUrl(), $endpoint));
         $headers["Content-Type"] = "application/json";
         $headers["Accept"] = "application/json";
 
@@ -47,7 +47,7 @@ public function request(string $method, string $endpoint, array $params = [], ar
         switch (strtolower($method)) {
             case 'post':
                 curl_setopt($curl, CURLOPT_POST, true);
-                curl_setopt($curl, CURLOPT_POSTFIELDS,  $httpBody);
+                curl_setopt($curl, CURLOPT_POSTFIELDS, json_encode($params));
 
                 break;
             case 'get':