Zytech Solar interview questions

Whole recruitmemt process was blunder they told me they are willing to take me in their company as a digital marketing manager, their managing director signed the offer letter which i still have till this day, I told them I can only join after resigning and completing my notice period in my current firm, their managing director said okay and signed the offer letter, but once I reached them after completing the notice period they said in a totally unprofessional manner that they already hired someone, now I lost my job which was going fine and I was on the edge of promotion in my previous firm. I have my family to feed Whole family burden is on me.