Nokia Asha on AT&T without data plan

I have a family member with a crappy feature phone on AT&T who really wants an upgrade. She doesn't want to pay for a data plan, but she'd like something more durable and responsive. The feature phones AT&T offers are all laggy and cheap, so I'd like to buy her a Nokia Asha 311 from eBay and put her SIM in it. I've read that AT&T won't detect it as a smartphone or automatically add a data plan.

Has anyone had experience with this before? I know the Asha comes with Wi-Fi, and since that's all she'll need, I don't want her accidentally getting charged per KB for accidental data. Can you disable mobile data completely without also blocking MMS? (I've tried something similar before with an unlocked Android phone, but it was very frustrating since data kept "leaking" through and racking up charges.)

Thanks for the help!