online loan taken out by my daughter

:x My daughter took out a $500.00 signature loan online.They were taking the payments out of her checking account and come to find out,ALL the payments they had taken out were going towards interest only! She was never told this until the company she borrowed the money from folded and this other company took over.They told her she had to pay the loan off completely or they would prosecute her,press federal charges on her and put her in jail.She sent them $1800.00 and they STILL want more money.They have called almost every member of our family from four different states and are rude,threatening and aggressive to all of us.We have no idea how they got our numbers and even my mothers cell phone number.They call when family is at work,at night,etc.They will not tell us what they want.We DO NOT need this crap right now as we are dealing with a serious medical condition concerning my brother(he has recently been undergoing chemo,due to a cancer diagnosis) and the one guy called while we were at the hospital yesterday while he was taking his treatment.How is it legal for them to call all of us after we have asked them not to? And I don't see how she could STILL owe them money after she has paid all of this.PLEASE HELP!!!!!!!