There's a dahlia listed at High Desert dahlias in Wa state called Wittam- could be what you're looking for - it's white- perhaps the person who helped you didn't know the correct spelling. Have a look-- they're not taking orders now but you can probably order from them sometime in the late winter/early spring.

Here is a link that might be useful: High Desert Dahlias

Thank you plantlady2 you may be right and I'm going into the site right now when I'm finish this message?