i din get the end...

a few reasons:

He couldn't read the letter, so he didn't even know he was being given the millions;

it was more important to him to pick up Pooja on time, than figure out what this lawyer wanted;

he was so content with his life that even if he knew, he just might have refused the money (I think, anyway).

He couldn't read so didn't know what the letter said. This point was touched upon twice - once by the little girl (who Amal gave the letter to) and boy outside the house and then again by the man who left the money to Amal in his voice over at the end. Perhaps you should pay more attention.