DH had this happen recently. I got a collection notice for a cell bill in California--neither of us has stepped foot in California for over 30 years! Contact the credit bureaus immediately and file a fraud report. Put a hold on your credit. Order reports and look them over carefully, then dispute anything that's not yours.
And, according to the Fair Debt Collection Act, if you inform a caller that the debt is not yours and you do not want them to call you, they legally cannot call you anymore. Google the Fair Debt Collection Act and read it carefully. Then mention it when you receive a call....that usually shuts them down right away.
But you must be sure these accounts are not on your record...don't hesitate, go to the credit bureau sites and submit a dispute right away.