Changing Text on the Contact Form Button

Hello,
Am using the latest version of NF along with other plugins & themes.

My question is :

I am using the GeoDirectory Contact form from Ninja Forms drop-down. When i use this form, a button is displayed “Contact FOrm”. I am using the shortcode to dispaly this button. which is

[gd_ninja_forms form_id=”4″ text=”Contact Form” post_contact=”1″ output=”button”]

Now in the text value above, instead of “Contact Form”, i need to display the First Name of the lister as in “Contact First Name”.

Can you please help me with this?

Appreciate your reply.
Regards/Manish