old dept ben snyders dept.store which was paid in 93

Obviously, you need to get them to verify the account. Often, even if it is paid off, it's hard to prove it because it is something you did 15 years ago and you have probably tossed your proof into the trash. Whatever the case, the SOL has most likely to have run out anyway.

Get the collection agency address, the agent's name and the account number. Write them a "cease and desist" letter, telling them to stop calling you. Send it "certified, return receipt requested" (so you can prove they received it). It is quite possible that you will not hear from them again.

I read that there are collection companies purchasing these old debts (some of them invalid) in bulk, for just pennies. Even though the SOL may have passed, they can still try to collect. Obviously, if they did not collect some of the money, they would not be purchasing this stuff.