Is your cellphone number on the National Do Not Call list?
https://www.donotcall.gov/
If it is and has been more than 31 days then you can lodge a complaint, even if its your own cellphone company sending the messages. I have had all my phone numbers, even my skype-in number, on the list for years. I never receive telemarketing calls and have never received an unsolicited text message. During elections I receive sequential dialing messages from political campaigns but they are often considered charitable organizations and exempt from the do not call list.