Resign from the company when Manager and HR not sending acceptance of resignation and last work date

I'm currently serving a notice period in an IT company. The actual notice period is 90 days. I informed the manager and put a notice last month through the ERP system. I told him that I wish to resign earlier by 60 days. As per the ERP system, the last working date is 90 days from the date of the notice. Now, it's been around 45 days and still, I've not received any mail regarding resignation acceptance and the last working date. I sent many reminder emails regarding this copying respective HR people too. Still, I received no response. I called several times to HR. HR asked me to reach Manager regarding this. When I called him, he cut calls and no answers. Last week, I called my manager and told him that I couldn't support him for the next month and asked him for an earlier release. He asked me to work more on the deliverables in the upcoming days till next month so that he could relieve me earlier. I told okay, but I didn't receive any acceptance mail and the LWD. He had plans to give me new works and asked me to put more effort from now. I am not properly assigned the position in the project as of now and I don't know what are deliverables that he is planning for. All the works are associated with software development modules, which require more time and effort. But, he is insisting to spend extended hours daily along with other developers. When I call HR people, they just asking me to reach Manager. When I ask Manager, he just replies that he will do it. I am just working as a shadow resource or buffer. I am not provided with any resources. I have not signed any contracts with the client. I have not communicated anything about my role and responsibilities. Let me know any solution as I have more than 2 years of experience with my current firm. I am planning for resignation by 60 days from the date of the notice. Still, I am having only 15 days left.