Do I have a lawsuit if my sister slandered my mother's funeral service that I paid?

I paid for my mother's funeral with an at-need, preened contract with a life insurance policy. My sister was with me while I was making arrangements. She and the director new one another. They have done other bad things. The FD did not give me a receipt, Statement of Goods and Services selected.2 years ,later I went to get a receipt, he gave me a copy of (statement of goods,and service selected)it was in her name. I got upset and then he printed out a new one that had 1 cent higher sales tax - the current tax! and back dated it and signed it. The total did not match the insurance assignment. I currently have an investigation going on with the board of funeral service. They got another (statement of goods and service selected) with the tax and the assignment right. and my exact signature from the one he gave me before exact overlay. Do I have a civil lawsuit? My sister told everyone that she had to get a loan to pay for the funeral and slandered me four years to my family.