No you cannot. Unfortunately a voice plan is required.
6.3 What Are The Voice And Data Plan Requirements?
A voice plan is required on all voice-capable Devices, unless specifically noted otherwise in the terms governing your plan.
An eligible tiered pricing data plan is required for certain Devices, including iPhones and other designated Smartphones. Eligible voice and tiered pricing data plans cover voice and data usage in the U.S. and do not cover International voice and data usage and charges. If it is determined that you are using a voice-capable Device without a voice plan, or that you are using an iPhone or designated Smartphone without an eligible voice and tiered data plan, AT&T reserves the right to switch you to the required plan or plans and bill you the appropriate monthly fees.