3g coverage

i'm a bit surprised that i don't get any 3g access at my workplace. 3g on the iphone works at my workplace. so does 3g on sprint and 3g on t-mobile. but 3g using my ipad in my workplace shows no coverage. as soon as i go outside, i get 3g coverage. i'm pretty upset about this as i was waiting for my 3g ipad so i could use the ipad at work. now i find i can't get access to the internet using att 3g on the ipad. does anyone know why?

i get 3g at home where my sprint cellphone gets very poor reception but my sprint phone works fine at work but the 3g ipad doesn't work. go figure. any advice?