picked up the phone but no answer from their end

I have noticed this number coming up on other unwanted phone call lists.  I do not answer calls that I do not recognize. Thankfully, no message was left so it won't cut into my minutes.

Got a missed call from this number, tried it back and it was busy.  No message was left, so I don't know who this is, but if it is a sales call, this number is on the do not call list and has been renewed every quarter to make sure that I do not get sales calls on this phone.

I also received a call from this number.  No message.