You have to have a data plan? I put in an existing AT&T 3G SIM I have had in 2 other devices besides the LG Thrive and I never had to have a plan. If I used Data it just deducted it from my $25.00 acct balance. But I think they freeze your data usage after your account balance gets below $10 or $5. I can still text, make and receive phone calls, but when I am out and about data doesn't work unless I am near WiFi because my balance is below $5. hehe