Does rent a center have the right to harass me about furniture and I am only a reference, not a co signer or renter?

My sis has been renting from Rent a center and used me as a reference. They called and I gave them the info they needed in order to loan their furniture...now that they have been unable to contact her, they are continuously calling and harassing me and I asked them 3 weeks ago to not call again. I mean, they literally took it as a joke and continuously called numerous times right after I had to hang up on them, to the point I had to just start answering and hanging up so that they can't leave anymore voice mails...I made them aware then that they need to handle their protocol because I don't even live in the same state as them in NY. All that I can do is forward the message over. I have all messages and calls in history. And they are still calling!! There has to be something I can do the protect myself from these harassing calls because they're not stopping just because I asked so I need help please!