Midland credit trying to threaten me

Midland credit sent me a letter. It states I owe them for a credit card worth $6,000. I never had that card, nor is it anywhere on my credit reports. Apparently it back from 2017. Since it’s been that long anyway, they really can’t do anything, but midland has been shady in the past to other people. They only giving me a week to respond, which is unreasonable as well. Do I call to dispute it or do I let them try to take further action and drag it court if they try to be shady?