When you send a text message that looks like it came from a phone number other than yours, it is known as SMS spoofing. Unless you have an iPhone running the SMS Veil app, it is impossible to send an anonymous text from your mobile phone. You can, though, easily send anonymous texts from a website designed to keep your identity protected.
Find a website that offers free anonymous text messaging/SMS spoofing. Some popular choices are AnonTxt.com, TxtDrop.com, TxtEmNow.com and TextForFree.net. These services can send anonymous texts to almost any country.
Type the recipient's mobile phone number into the Web form.
Enter a contact name, phone number or e-mail address (for replies). If you want to make it look like the text is coming from another number, simply enter that phone number. You can also just leave this line blank for total anonymity.
Enter the subject line for your text message.
Type the contents of your text message. Make it brief; texts are limited to 140 characters. Press "Send Message."
The recipient will have no idea whom the text message came from unless you entered a return phone number or e-mail address. The recipient can block receipt of any further anonymous text messages, so you may only be able to do this once.
While SMS spoofing can be fun, do not use these services to impersonate another person without her permission.