Legal notice during Probation period

I have received a legal notice from a company, when i left the company I was on probation period. I joined the company on 17th January and got suck leave from 16th February to 14 March as I went under serious health issues against which i submitted my summary and reports. I joined back on 14th March and resigned on 16th April due to toxic environment. There was no rules and employees were making it difficult for me to work including my boss. After having such a major health issue it became difficult for me to handle my mental peace because of my office environment. Now the company is asking for huge compensation and blamed me that i made a loss in project, I gave mental trauma to my boss, whereas my boss mentally harassed me Saying i can do nothing, i should get some shame i have zero knowledge that he will destroy my career. I want to know what can be the consequence as I have received legal notice on whats app and also my address is wrong Mentioned on legal notice. It has advocate stamp but no court stamp