Received a legal letter from SBI credit card- to pay dues taken by my Late father

Dear sir Today i received a legal notice from sbi credit card which states that on demand of Father, Mr. Vijay Wadhwa, credit card facility was granted and as such he had been availing the credit card facilities of SBI credit card since the date of issuance of the card. That Vijay Wadhwa had been availing credit card facilities granted by sbi subject to the terms and conditions of credit card agreement, Vijay Wadhwa had further undertaken to pay the bills raise by SBI which is outstanding as on date. That as per the provision of the cardholder agreement, the primary cardholder's estate would be liable for settling the outstanding in the case of deceased customer. That as per the accounts maintained by sbi in ordinary course of business, a sum of RS. 104,002.41/- was outstanding and payable. The advocate mentioned in the letter, "I, hereby finally call upon you, being legal heirs of Late Vijay Wadhwa, on behalf of my client SBI, to pay the said sum within 15 days of from receipt of this notice,.......etc etc" My father passed away in 2007 and nobody knows about the credit card. Also my father died of cancer and left no assets for us , in that case are we still liable to pay? pls advise