What if the boss doesn't approve the resignation? Can I resign by SMS?

If you want to resign, you can say nothing, but texting doesn't conform to the rules, just like the boss is eloquent but can't get a raise, so it is better and more secure to resign according to law. If you want to resign, you only need to submit a written notice of resignation to the company 30 days in advance, without the company's consent. If you continue to work for 30 days, you can apply to the company for resignation the next day, which will be handled by the company (Article 3 1 of the Labor Law), and at the same time pay off your salary in one lump sum and issue you a resignation certificate, otherwise the company will violate the law.