Never respond to them with the word "Yes". They will record your voice saying yes and then they will use it to say that you agreed to purchase a non-existent service from them.
Got a call on my government-issued cell phone at 1:08pm on 7/26/17. I had no choice but to answer as this is my job phone and I am not allowed to ignore it. There was dead silence and then they hung up. I cannot believe I am getting scam calls on a government-issued cell phone.