What to do when you are getting calls from Sallie Mae phone number

Need to know Sallie Mae Phone Number:
We started receiving calls yesterday from 866-558-6255. They called four times over the course of the day and no one was home and they didn't leave any messages. They started calling this morning at 8:07, 8:52, 9:42, 9:43, 10:57 and 11:14 a.m. Needless to say they woke us up with the first two calls. My husband finally answered the third one at 9:42 and they asked for a Logan Hughes. My husband informed them they had the wrong number and then they asked if he knew a Logan Hughes, which he told them no and said, "Don't call me any more". Then the guy called him right back at 9:43! My husband answered, "I just told you no one by that name lives here and we don't know anyone by that name. If you call me again, I'm reporting you to the FCC!!!" and hung up. So then we left to get breakfast and came back and they called again, which we didn't answer. So he was on the house phone and I Googled the number and came up with Sallie Mae, so I called them on my cell. They just answered, "Hello?". I explained what was going on and the woman asked if anyone in the house had an account with Sallie Mae. I told her that I had just signed up to get information about college for my daughter, but that was the extent of our contact with a Sallie Mae. She said she had two numbers in their system for this Logan Hughes and she would mark ours as a bad number and apologized. O.K. - it's over! Then they call back at 11:14!!! I answered and they asked for Logan Hughes. I said, "I just called this number back and spoke to someone and told them you have the wrong number. She said she was marking it as bad. Do you understand that you're violating the law?" And she said, "Oh wait, I see there's a "B" next to this number marking it as bad, but it takes up to 30 days until it's removed from the system. I'll make a notation again".

I was blown away! So your now telling me that you're going to continue to call us for the next 30 days?????? I'm sending them a cease and desist letter if I can find an address for them. Even if I did have a debt with them, calling 6 times in the span of 3 hours is a bit much.