Courts in Central China’s Henan province have been getting debtors to pay up by using a customized ringing tone service, Zhengzhou Evening News reported on Friday.

The service alters the sound that callers hear when they try to contact debtors, replacing it with a message that says how much the debtors owe.

More than 20 debtors have been targeted using the service, which has produced good results so far, according to the courts.

One debtor, surnamed Liu, was referred to a court in Zhongmu county, Zhengzhou, in February because he owed 40,000 yuan ($5,900).

After being targeted by the service he went to court and offered to pay his debts immediately so that the messages would stop.