Notice period days not mentioned in my offer letter

Hi Sir/Mam, I worked for 2 years in a Automotive organisation. I am going to switch over to the new job in another organisation. In my previous company offer letter, they didn't mentioned anything to serve notice period for 90 days. My next comapny gave 45 days after offer need to join in their organisation. Here, my old company forcing me to serve notice period of 90 days and they are saying we told you to serve 90 days notice during induction program. I didn't remember did they mention it or not? And Now I joined in new company, the old company asking 29k rupees to get relieving letter. I cant tell it to current company to claim the buyout. Because the HR Said you should told before joining like that. But my current company didn't tell you have to pay and go the notice amount like that .. But they didn't open their mouth while I served in notice period. and please you guide how should i get relieving letter ? i am in depression that what can i do next? i cant afford much amount