Trying to collect debt that isn't accurate

by Rich
(Tampa, FL)

My wife recently received a debt collection notice from an agency in Michigan stating she owes $1355 to Bally fitness. She canceled that membership 10 years ago in good standing. We checked all her credit reports and this does not appear on them, her credit appears to be quite good. What should we do next to stop this in its tracks?

Interestingly the notice went to her work address, not home.
Thanks