You've mentioned in your question that the intended statement is "Know your customers' needs before they even talk to you". Here, your customers can refer to either:
a) People who haven't been talking at all, in which case, they aren't yet customers, but are valid prospects / likely customers
b) People who are existing customers & talk from time to time, presumably on a need-to basis.
In the former case - if they aren't yet customers- Know your customers' needs even before they turn into your customers is one way of saying it. ( No idea about your space constraint, you might have to edit elsewhere to make space or find another workaround to accommodate it if you the sound of this.)
In latter case - if they are existing customers- Know your customers' needs beforehand might do.