Work Change on E-7

Hello everyone! I have an E-7 visa here in Korea and been working for around 3 months in my company now. I work in international sales, as a specialist. After the prohibition period I though we'd talk about my salary again since it is remarkable low for what I am doing and this is what we agreed to do on my interview, looks like they have no intention whatsoever to recinsider my salary. I talked with the HR a few times and informed them about my concerns but somehow they always went around it and the conversation always ends in "if you work harder your salary will go higher". I know I am doing a good job and I know I am getting paid 1.5, nearly 2 times less than I should be paid right now looking into the position and my responsibilities in Korea. At this rate, I am concerned about how I can manage my living in a few months actually. Do you have any ideas about what I can do about this, what and how can I talk with my bosses/HR? I really want to change my job to be completely honest but I know the change of job with an E-7 is so hard... Please share with me your thoughts or tips about what to do. Thanks in advance!