When you ’turn your back on somebody’ you are making it clear that you are abandoning them or refusing to help them. It can also mean to disassociate yourself from a group or individual. This expression usually has a negative connotation and can be used in both social and professional contexts.

1. Once Nicole made it big in the music industry, she turned her back on the people who had helped her get to that position.
2. I had to turn my back on a number of old friends who were not good for me and holding me back from reaching my goals.

1. Eric has been a loyal and productive worker for me for over a decade. I'm not just going to turn my back on him because he's had a poor few weeks.
2. Upper management have been turning their backs on the problem for years. It was only a matter of time before it blew up in their faces.