AU services and contract fault

Before October 2019 I stopped one of tree Contract with total monthly payment was about 7000 yen to AU kddi japan. After that the stopped contract was still active until March 2021 and monthly payment was about 12000 yen. I can not confirm this mistakes to AU even though they used translator and I didn't have any proves because I disposed the contract. I tried to get information from au translator but it seemed they didn't care and just try to help stopping all my contracts. I also paid unlocking services but my phones are unlocked until now. How could we get a written explanation about this from AU japan?

If you actually disposed your contract at some point, you should have a copy of the paper (when you did it at their shop) or an e-mail (when you did it online). No problem. Show it to them.

Considering how cheaply a person can get mobile phone service these days, AU KDDI was really taking you to the cleaners with that old contract of 12,000 yen a month.

I've heard a lot of horror stories about contracts with AU and SoftBank. Unless you can prove cancellation, they will want all their money. In addition, it is said the person will also be put on a blacklist until payment or the debt is settled.