Amcol to DataSearch, Inc????

[Xstix]

After making payments as agreed on time by bank autodraft for a couple years to Amcol for a substantial medical bill, today I received a collection letter from Datasearch, Inc.  The statement is for the balance of what my last balance to Amcol was.   Datasearch is saying "your delinquent account has been placed with our collection agency for collection in full".  Is that even legal if payments have been made on time? Do I contact Amcol or Datasearch or a lawyer?

[Anonymous]

Amcol directly. They have been good about medical bills and agreements. You can even email the CEO. They responded to me when I had medical bills in collection. 

[Xstix]

Contacted Amcol directly and was informed the original creditor (The hospital) took the debit back and it was no longer in Amcol's control.  Apparently then it was reassigned to Datasearch, Inc by the original creditor?  I received no notification or was made aware of any of this taking place.  Can they even do that legally and force payment in full after making the agreed payments to Amcol every month for more then 2 years?  This seems fishy.  I'm in Texas if they makes any difference.