As you know while calling to me yesterday

[Lee12jan]

Dear teachers:

When I write a email to someone, I'd like to tell him
that he already knew it when he called me yesterday.
Could I simplify it as following:

====================================
...as you know while calling to me yesterday...
====================================

[Mister Micawber]

.
as you knew when you called me yesterday...
.
_________________
Native English teacher at Mister Micawber's