Since you are not the co-signer of the student loan of your estranged child but are tired of the calls from debt collection companies for unpaid money, you have the following options:1. tell and write the debt collection representative to not call you any more. Keep a copy of the letter for future use and need.2. change your telephone number.The statute if limitations for breach of a written contract ordinarily is four (4) years from the date of the breach.