Unable To Call My Daughter. I Get A Busy Signal.

I have had StraightTalk as my cell phone Provider since may and since that time I have been unable to call my daughter's #.  When I do I get a quick busy signal and then my phone hangs up.  I have a Samsung Galaxy SII S959G phone and my daughter has an IPhone and she has CellCom as her cell phone provider out of DePere, WI.  I talked to CellCom and they say it isn't them but StraightTalk says that it is.  I didn't have this problem until I switched to StraightTalk and my Samsung Galaxy SII phone.  Cellcom is working on it but do not think that it is them.  What should I do at this point.  My phone # is 920-948-2875.  I was ported in to StraightTalk from USCellular when this started.