How does foreign debt work on a personal scale

So I was overseas in japan for two years and I had to leave due to some family matters back home. My wallet was stolen shortly after with the debit card that linked my phone bill in japan. Now I’ve tried canceling it online but the damn website was all in Japanese. My phone was detached from the service there but my phone that doesn’t work on America still needed to be paid off so I’m guessing I owe them 500$ or so. I haven’t received any kind of notification or anything so I don’t know how long these things last for in japan before they forget about the debt. If I ever want to back on a vacation or so.