To see is to believe. You can't get everything by emails and calls only, equivalently means they can't make you successful all the time.
If you want to fight for wins in business world, you have to show something real, something special and more competitive than other people.
One of the best strategies is to get your customers involved in the firsthand experience. People would get used to listen what they would like to hear, which full of interest but they won't tell you sometimes! To show your sincerity and enthusiasm, why not invite your customers to your company and have a few "experience lessons"?
What the picture shows above is our customers doing some testing by themselves. They can clearly know how is the strength of the plastic formwork which meets their requirement.
Try to provide your customers with greater support, treating them well just like your best friends.
Nowadays, business is no longer about profession only, as it's more about caring, emotion & interaction.