This number sent me a text message stating:
[T-Mobile: Your account was used to sign in to a browser, We've noticed significant changes in your account activity, go to security https://verifyaccount-t-mobile.com/?addbilling Please do not reply to this messafe, if you need help, please reach out to us by dialing 611 from your T-Mobile phone, or calling 1-800-937-8997]
This is not from T-Mobile