[Q] unlocking s4 SM-S975L - help please topic

hi,
couldn't find a solution anywhere, so i'm trying here, apologies if i misplaced my post.
i bought a s4 SM-S975L from wallmart (straightalk) in the US, but got relocated by my employer to israel.
now im stationed in israel/malta (rotating).

the s4 SM-S975L is locked apparently for any sim. tried to contact the company - they blew me off.
now im stuck with a phone which i cant use.

does anyone know how to "sim unlock" this one?

please?

thank you

dima.reiderman@gmail.com