what tech does my phone carrier use? GSM, LTE?

hi, i want to buy HTC One from USA and i live in iraq,

HTC says the One will on "GSM/GPRS/EDGE: 850/900/1800/1900 MHz"

but how can i know what does my phone's carrier is using?

i already called the Customer Service and they had NO idea, and their website does NOT provide any info

is there any way that i could figure out on the phone? (Galaxy Nexus, S3, Lumia 820) i have it in the house so can i just download an app and tell me the info, or on android dial a diagnostics number ??