translation incomplete

Hi,

I’m using the couponpresstheme and want my site to be in Dutch.
There is an option within the theme to translate fields into your required language. However, this list is incomplete.
I still find english language on my site.
For instance, when you create a new coupon you fill out the expirydate. Lets say I chose no expirydate. When you go to the site and look at that coupon you see the word NEVER (as in never expires). How can I change that. And there are more fields that you cannot translate in your wordpress menu (general settings , language).