
Why didn't he just phone Conan that "someone sent a letter to Shinichi-niisan"

Heiji is a well-known high school detective, so it's normal for Okiya to know him.
But what I'm wondering is: why didn't Okiya choose the easy way : just phone Conan

Why did he think that HEIJI COULD solve the problem?
Why did he think that HEIJI would be able to contact Shinichi?
That's the point !