What if I don't pay for my journal subscription?
Why don't you pay your journal subscription?
There was an error in their records so I get it for free.
Taking the subscription for free is the same as stealing, it isn't right. You should tell them about the error and start paying the fair price for your subscription.
It's not my fault that they made a mistake. The only reason I'm using it is that I can't pay for the journal on my own.
It would be appropriate to let the company that provides the Journal know about the error. It's wrong to take advantage of someone's mistake.