Explain very nicely how you can achieve what your bad customer would like for fee or upgraded plan. In fact, tell them that you'd love to do it but you would ne

Explain very nicely how you can achieve what your bad customer would like for fee or upgraded plan. In fact, tell them that you'd love to do it but you would need to direct new resources toward that effort. Make sure that fee is a healthy one that will either make them go away or make the effort worth it for you. Win/win.