Yes, there are several ways in which it is possible to send text messages through numbers that don’t belong to you. Potentially, cell phones and/or SIM cards can be cloned, and the clone will then be able to send messages that appear as if they are coming from the original phone. However, if a phone provider recognises that this is going on, it is usually quick to block either both SIMs or at least the original, presumably legitimate phone account, as the practice is of at least dubious legality. Easier and far less technologically demanding, there are several online services which allow users to send text messages. They require the user to enter a cell phone number from which the messages can be sent. They do not actually require proof that the number entered belongs to the person requesting the service, so one user could enter the cell phone number of another, and then send whatever messages they like via that number.
