Employer asked to serve 60 days notice period however no appointment letter is issued to me

Hello sir, Date:- 30/12/2021 I got job offer letter from ABC ptv. Ltd ( Its 10 year old small company having 50 employees) on 28th Aug 2021. I accepted the same and accepted to join on 26th Oct 2021. In the offer letter it was mentioned that i will be given appointment letter at the time of joining and there was nothing mentioned regarding probation period. i have joined ABC Pvt. Ltd. company in 26th Oct 2021. On the day of joining they informed me of 3 months of probation period after that only i will be considered as legle employee and appointment letter was not issued to me. After almost 2 months i got job offer form XYZ company and i submitted my registration letter to Sparrow risk management Pvt. Ltd. on 29th December 2021 stating my last working day as 25th January 2021. However my employer said there is a notice period of 60 days and i have to serve that. in the response i wrote that i haven't been given any appointment letter nither any policy documents given to me state the information of notice period nither i have signed any documents which clearly mention about notice period and above all i am probation period. Keeping all the things in mind i am not bound so serve any notice period however I am ready to serve 30 days for smooth hand over take over. However the organization is not accepting the same and threatening me to take action i dont serve 60 days or min of 45 days. It seems like they won't issue an experience letter/reliving letter and will not clear my dues. Kindly help me what action should i take as of now to not get involved in any trouble and able to take my experience certificate. and even in case it goes into legle matter what care i should take as of now.