No OTA Antenna

[voom1]

I got Voom installed last Tuesday but the installer did not install a OTA antenna. My question is should he install the OTA antenna even if i get only one channel? I called Voom and they told me I could not get any local channels and that is why I did not get a OTA antenna. Is this correct? I checked all the sites on the internet and all of them showed that I should get NBC. Who can I call to get the antenna installed. By the way, all TV stations are 21 miles away and all are digital.