Back pay from hagwon

I have recently finished a year of work at a hagwon, but unfortunately, I have not received my severance pay. My former employer has informed me that they have no intention of paying it and stated that employers have the option not to pay severance. Could you please advise me on the laws governing severance payment? I am seeking justice in Busan. Employees in South Korea are entitled to severance pay of at least the "average" wages for not less than 30 days for each continuous year of employment, prorated for portions of years worked. The "average wage" is calculated based on the average compensation received by the employee over the three months preceding termination. Severance payment is a right that cannot be waived by contract and must be paid within 14 days of termination. If not paid, the employer may face civil and criminal penalties. Filing a claim at the local Labor Office is a simple and effective way to enforce the right to severance pay, but it is advisable to speak with the employer first. However, if the situation is not resolved, filing a claim may be necessary.