Can company enforce notice period not in signed agreement?

I recently joined one company in which I got offer in offer they have mentioned I have a three months probation period and I have signed employment agreement and haven't read it but in employee agreement they did not mentioned probation period and after 2 months have resigned but as per employee agreement they are asking me to pay 3 month salary or I have to serve three month notice period so how can I handle this situation without paying any money or without serving notice period