Verizon HTC Droid DNA to ATT

Hi,

I recently switched from Verion to ATT, I kept my Verizon DNA and put an ATT SIM card in it. It works fine for calling and texting, but I cannot access the ATT newtwork mobile data. Is there a setting I need to change or add an APN? Currently the only APN on the phone is VZWinternet, and the phone won't let me connect to the internet except through WiFi.

Thanks Richard