PNC Mortgage Completed short sale with PNC who refuses to release lien on property and ruining my credit!! Pittsburgh, Pennsylvania

I completed a short sale with a HELOC loan held by PNC in 2010.  I was represented by an attorney.  PNC and I signed an agreement that for $2,000, they would accept the short sale and release the HELOC lien on the property.  I gave them $2,000 and title insurance was issued for a free and clear title.   To this day, they refuse to release the lien on the property.  

According to county records, there is still a lien on the property from PNC.  I've called them several times and have showed them the signed agreement and they are ignoring me.  The title company is also trying to get them to release the title and they are not cooperating.  I've been sent to collections and they are threatening to foreclose on the property with the new owner living in it.  They are not returning any of my calls or emails.