fix error mobile

helper/refill/util.php

@@ -15,7 +15,7 @@ class util
             "188","187","182","183","184","178","130","131","132","156","155","186","185",
             "176","133","153","189","180","181","177"];
 
-        $pos = mt_rand(0,count($prefix));
+        $pos = mt_rand(0,count($prefix) - 1);
         $no = "{$prefix[$pos]}" . mt_rand(10000000, 99999999);
 
         return $no;