Forgot to deactivate my Internet [Wind] when in Italy
 

and I am home [India] now. Any way that I can deactivate my plan? I want to use the card again for next year.

Plan was; Mega Unlimited, 10GB/Month

Can I send a SMS to 4033 from here? If so, should I just add the country prefix?

I have an online account. Is there any way to deactivate from there?

There is a 'Renew' option next to my Mega Unlimited. Does that mean that it will NOT automatically renew? [Pic attached].

Sorry for the very late reply.
I suppose the only way to deactivate is sending the SMS to 4033 writing "UNLIMITED NO". You don't have to add an international prefix. Of course the SMS won't be free.