MBD debt collectors harassing me!

This company is now harassing me. Since late Feb this year they have been hounding me looking fir my mom whom I told them is deceased. I sent them the death certificate and they acknowledged it. Every single day this company phones me still looking for my mom! How many times do they need her death certificate? How many more phone calls? This is harassment I keep telling them to stop phoning me! I am suppose to be mourning my mom , instead I'm getting harassed by a company that I have told a thousand times my mom is dead