Who called from 3604604346

Both my boyfriend and myself received calls a few minutes apart.  His number is new but mine has been on the do no call list for a long time.  Doesn't seem to stop them!

Here in saint Louis Missouri got a call around 12 from this number didnt answer but everytime I called back it was busy. Number going under Don't Answer in my phone

I received this on my cell phone but did not answer because I did not recognize it and did not want to pay for the minutes and it is outside my local calling area for calling back on my land line.

It seems  they called me before back in November.

Called my cell, PA number. Left a blank voicemail and hung up. Called back to receive a busy signal. How /why do these things call cell phones? :/