Repeated SMS messages from 74611888

The past few days I've received texts from 74611888 saying:

AT&T msg: Use this one-time verification code to complete sign-in: 568262  We'll never call, email, or text you for this code.

and

<#> AT&T Free Message: Your temporary PIN is 799712 

 IOpMWSEeQxt

I doubt these are actually from AT&T because I haven't initiated anything that would trigger such a response.

I tried reporting these to SPAM but the source isn't a phone number or a valid short code. Where can we report these?

Thanks!