I am working in a private sector company. I have received an offer letter, an appointment letter, and all the facilities from the company. The main problem is the manager's attitude towards juniors, which is quite uneasy. I have a better job offer now, but the new company requires me to join as soon as possible, perhaps in 3 to 4 days. However, I am bound by a notice period of 15 days. Please advise me on how to resign from my current job so that I can join my new job promptly.