Hi there! @ButtonMasher thanks for posting your concerns. Unfortunately because of the nature of the service you have, there is no way to turn those notifications off.
You can migrate to an AT&T post-paid account to avoid those messages. This can be done at AT&T company store.
To locate your nearest store please go to www.att.com and select Store Locations & Appointments on the upper right of the site. From there you can enter your zip code and find your nearest store address, hours of operation and phone number.
Thanks!
Charise