Do I have a case to sue for harassment?

There is a local auto dealership that calls about every month about buying back a car that we rented in 2010. They ask for my husband who died in 2012. We had the car for 12 hours. They’ve been either calling or mailing asking to buy back the car. I explain the situation and ask that they remove my and my husband’s name from their list. It’s becoming upsetting to me when they ask to speak with my husband. When does this become harassment?