How can I get management to notice all the things we do to help the company to increase sales and remain profitable?

Answer: I am not sure you meant to say that the credit department was responsible for your company's profitability. I would suggest that you take time to document your achievements and successes; employers usually do a good job of documenting errors and oversights and a poor job of documenting the ways in which the credit department helps the company to avoid problem accounts and to encourage sales to creditworthy customers and applicants.