Very professional looking.
But as already stated, white shirts will get dirty very quickly unless they are doing regular office or shop cleaning.
I'm in 2 minds about the phone number with my shirts too. You very rarely see phone numbers on the shirts of big companies. They look at it as coporate image rather than advertising. So by NOT having the number you coul be giving the impression of being bigger.
Website address under the back logo might work well though.....
Regards
Mr H