401K rollover IRA mistake with after tax money

In 2013, I rollover my 401K to an IRA, but the 401K had after tax money.  I contracted the company that is holding my IRA account and they indicate they can't recharacterize the after tax money to an Roth IRA account.  What do I need to do so I don't pay taxes when I withdraw the after tax money from the IRA account?