what is the meaning of these calls?

no message left.  I receive a call from this number a couple of times a month

no message left

i just got a call from them and i try to call back and itsd busy. its so annoying. twice ive changed my number to avoid these calls.

I recieved a call from them for my 18 year old daughter.  A lady with a southern accent said that she won a sweepstake.  I said I would like more information.  I was told that since my daughter is 18 they did not have to tell me anything.  I said that this was my phone number and they were not to call any more.  The southern lady said I was not raised properly by my mother and hung up.