Calling Business Logic Layer Method From PageMethods?

I've a static page method in web form application and I want to call method on private class level variable from it as shown below. I'm using jQuery to call the page method.

private readonly ICatalogBLL _catalogBLL = new CatalogBLL();
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
_catalogBLL.GetSomething();
}
}
[WebMethod]
public static UpdateSomething(int i)
{
//Want to do as below. But can't call it from a static method.
_catalogBLL.UpdateSomething();
}

UPDATE If I call it as said by John Saunders, won't it use the same instance for requests from different users as it is within a static method?