Please suggest

Respected Sir/Madam, My first job was in a ngo and from the very first day the program manager started insulting me in each and every situation. According to the appointment letter my reporting place was in the head office and I was told to travel extensively in 2 districts but later they claimed that I have to stay in such a location for every week 4-5 days where I am unsafe. If I travel regularly I would not be given travelling allowances. meanwhile in the office there was such a culture that any one can shout at me anytime. I got a new opportunity and resigned from my post within one day and I also gave all the documents which I had. Now the organisation is claiming and threatening me each and every day via whtsapp, phone call and emails that I have not submitted the documents. they also called my new director to talk against me. I have prove against them of mental harassment. Now please suggest me how to deal with them. they are crossing their limits everyday. And is this legal to leave an organisation in a short notice in probation period?