Mobile phones are by now fairly cheap and all too common, having now become a curse in themselves. While they can be a bloody nuisance their worth in sending along spells shouldn't be underestimated.
Even if you don't have a mobile there are lots of options to pass on a curse through the various homepages that offer free sms/pager service.
Anyway, it would be preferably to use one of these services rather than relying on your own mobile since with SMS's you'll also send your number, even when you have disabled sending it with regular calls.
You create a curse simply by making a statement of intent and sigilising it. Keep in mind that the sigil should be as simple as possible so that you can recreate it in ASCII code.
Alternatively you can create a mantra instead of a sigil and send this to the lucky recipient.
When you've entered the ASCII graphic or the mantra, charge it by any means of gnosis you find appropriate and hit the send button. The recipient should get the sigil within a couple of minutes. He will wonder what that should actually be and thereby it will enter his subconsciousness and start to work.