Hello nico3000, Technically yes, it is possible, it is actually possible to "customize the sender" of a text message. But be careful, identity theft is illegal, but for example, if you have no credit left, you can use a friend's phone and make it look like you sent it.
Personally, I have already tested it on http://sms.nandarion.info/ and it worked. There may be other ways, I don't know.
there's no site like that but free (11 years later lol)