Since your question is in the "Employment / Labor" section, I assume you are speaking as an employee. If someone at your work is sending text messages which have a sexual tone, ask/demand sexual favors, you need to report that to the Human Resources department. If you employer does NOT do anything to stop this you may be able to file a discrimination complaint under EEOC or your state's human rights commission.
Once you report this violation to the Human Resources depart you must allow them sufficient time to investigate the issue, meet with the offender, and come to a decision. That time can be a few months.
If you are not an employee: if you are a minor, report this to your parents, your school. If you are an adult and are getting unsolicited messages you can file a complaint with the police if the messages are threatening.
