"to bob 1999.................We don't choose God, God chooses us.
Why does he choose some and rejects the others?
I thought he loved everyone and there was no partiality on his part."
In Romans 9 Paul explains that God said He loved Jacob but hated Esau "though they were not yet born and had done nothing either good or bad"
Then Paul assumes the reader will ask the question you ask "Is there injustice on God's part?"
Paul, using a quote from the OT "I [God] will have mercy on whom I have mercy" and makes the point that God is the one who is sovereign, not man. Not the clay but the potter.
Later in the chapter Paul assumes that the reader will ask your other question. If it's not up to man but up to God "Why does he [God] still find fault? For who can resist His will?"
Paul answers the question by first asking "who are you, a man, to question God?". (God is sovereign, man is not. The game is played God's way not ours.)
Then Paul makes it clear that the potter has all the power over the clay. Not the other way around as you seem to want it.
Romans 9:16 "For it [salvation] depends not upon man's will or work, but upon God's mercy".
Peace