legal notice

The legal notice has received to my friend after four month of leaving job. Due to some personal family issue he had to leave the job. But the company has neither provided the last month salary. The day before he left, the company has appointed a new lady in his position. How can they send a notice of paying two months of salary or a huge amount. Are their any section to defend against them or what is the next step I need to do. Please send me an urgent review they have given two more days