fix bug

helper/refill/ProviderManager.php

@@ -281,14 +281,14 @@ class ProviderManager
         try
         {
             $file = BASE_HELPER_RAPI_PATH . "/{$name}/RefillCallBack.php";
-            if(file_exists($file)){
+            if(!file_exists($file)){
                 Log::record("provider callback api file={$file} not exist.",Log::DEBUG);
                 return false;
             } else {
                 require_once($file);
                 Log::record("file={$file} load success.",Log::DEBUG);
             }
-            
+
             $class_name = "refill\\{$name}\\RefillCallBack";
             if (class_exists($class_name, false)) {
                 $caller = new $class_name();