Why does the battery light keep coming on and car dying?

What is your question?

Replaced battery twice ( was told at dealership battery was not big enough) ordered the recommended battery through GM. Battery will not hold charge. Will hold charge for 1 to 2 days. Also replaced alternator, same issue, not holding charge. No one around here works on them and can't afford to keep taking back if not solving problem . What else could it be?