Hello @Amberamber0909!
Thank you for reaching out to us on the Community Forums! I can definitely understand your concern with MMS messages to or from an unknown number, and I’d be glad to help look into this.
You can check your usage on the My ATT for the date and time the message were sent or received. On your My ATT, please go to Usage. You will see an overview of your recent usage. Select, View Data, Text, and Talk logs in the Usage options section below the graph. Once there, select your device and choose the billing period accordingly to view the messages. Unfortunately, we do not have the ability to see which app the MMS was downloaded from or uploaded to.
Thank you for your time!
Donna, AT&T Community Specialist