Hi,
maybe it's a little redundant now, but this is my idea (worked for me).
It's a quite simple one : you use your arduino as a client, and an altervista site as the server.
In altervista site you create a page in which you can submit a command, the command will be written in another page of the site.
Your arduino will constatly check for new messages in this page (add a message counter, so your arduino will recognize the same order sent multiple times).
If you want, i may "borrow" you my site, it's already ready to be used.
Let me know if you need it 