I am 77. Since my full retirement age .at 65, I have continued to work part-time, although at much lower salaries than before retirement. Am I entitled to an increased SS payment for these years of work with payments into SS?

Roberta,
Your Social Security benefit is automatically recalculated every year that you report additional earnings on your Income Tax. If the new earnings are lager than any of the previously high 35 years of indexed earnings, then the lower year is replaced with the higher earnings and your benefit will be increased. If the new earnings are lower, then your benefit will not be increased.
Best,
Mike