You can get rid of data permanently as long as you don't have a contract with AT&T. If you have a two year contact there is not much you can do about it until it ends. If you have a postpaid monthly contract, terminate it, and start using a different carrier that uses the AT&T network.
These are the options you have that I am aware of:
AT&T pre-paid
Pure Prepaid
Pure TalkUSA
7-11 Speak Out wireless (be careful some use sprint and some AT&T)
Consumer Cellular
GTC wireless
Jolt Wireless
Locus Mobile (be careful some use Verizon and some AT&T)
TracFone (be careful they use multiple providers including AT&T)
Personally, on the phones I do not want data plans on I use Pure TalkUSA. You can buy a Sim only with minutes that rollover for $10 and as little as $10 a month to keep it going. For their family plan you can add another line for $5 a month.