Manager not accepting resignation

Hey guys, I am leaving this crap company and there is a 3 months notice, I have already served 6 weeks and till now the manager has not accepted my resignation. I resigned without any offer and he said why do you need acceptance if you don't have offer. He first said that he will relieve me early and that's why he didn't accept, because if he does then he won't be able to relieve me early. But today he told me that it's not possible for him to relieve me early and I asked him to accept the resignation again. He said that they accept resignation on the last week and I won't be able to take any holiday if I accept the resignation. I think he's full of sh*t, I'm scared that he may try to increase my notice if something happens, that's why he's not accepting, I don't know if he can legally do that. Do I need to give any explanation as to why I need him to accept it, I don't trust this a**hole one bit. I need him to accept it, how do I do it and can he say no I won't accept.