Resignation

Hi Sir/Ma'am, I work in an IT MNC. I joined this IT firm last year in October 2021 and I have currently completed 5 months. I joined this IT firm as a contractual employee for a big IT Organization. I have dropped my resignation via email to the HR and the HR's Manager on 15th March 2022 ie. Tuesday. The reason for my resignation is that after getting hired in this big IT organization, they have put us on bench. There is absolutely no work and no update from the company. When I text the HR, she doesn't respond or provide me any update. So, I decided to quit and look for better opportunities. Now, that I have received offer from another organization, I dropped my email but the HR is not responding to my resignation email or providing me any update. Everytime, I call the HR they keep making excuse that she will update me soon but never provides any update. Last week when I called the HR again, she got irritated and started yelling at me for disturbing her for updates all the time. But even I have to let my new company know as to when my last working day is at my current company but the current company is not giving me any response. It's been almost a week since I dropped my resignation but there has been no reply from the HR or the HR's manager. What should I do? PS: Also, I almost forgot to mention about my notice period. When I joined this company, in my Offer letter, the employer had clearly mentioned a notice period of 30 days and I had signed it. After, I joined the company, the HR Head sent us an email and updating us regarding the updated notice period which they have extended by another 15 days. So, now the notice period is 45 days instead of 30 days. However, I had signed on the 30 days notice period as per my offer letter. Can the employer just send an email stating that this email supersedes the previous offer letter since we never signed that. Please suggest what are my options and what can I do to get my release in 30 days instead of 45 days. Thanks and Regards.