Father passes away and I have been appointed Adminstratrix of his estate. He had a store credit card and my sister was an authorized user. I received a letter from collection attorneys for the credit card company stating that they are making a claim against the Estate for an unpaid balance. I requested proof and was sent months and months of transactions totaling approx. $20K. Most, but not all of the transactions took place after father's passing. I offered the collection attorney the amount due on the date of father's death. Collection attorney then returned debt to original creditor.

My question is: is the Estate responsible for the entire debt? Jurisdication is in Pennsylvania.