Legal notice from employer for not serving notice

I joined a company and left after first day. The company did not inform me about poor work facilities and lack of basic facilities. In my first day the HR informed me that washroom within office is for selected professionals (seniors) and Inuse the common one outside and so you do the same. He also informed me that there is no canteen and no pantry to eat food and one should eat food at the work desk. He also told me that you need to bring your own device laptop for doing company work on it and no depreciated value or anything against that will be provided. He also gave me 1 copy of appointment and forced me by sitting on my head to sign it without them signing it first. I had no other choice but to unwillingly sign it but I did half sign so that it does not match with my government documents, they said they will get but signed from directors but still did not give me a copy of the same. I requested them to leave me early on my first day due to my daughter's illness they agreed and I left. But after 2 days(weekend) I informed them officially via email about discontinuation statingnpersonal obligations. Now they have sent me legal notice claiming 3 months pay. I told them the sign is not genuine and I was not given my copy but they did not listen. What can be done? Pls.