Local courts have sentenced a total of 163 people to jail terms for 55 telecom scam cases involving 21.3 million yuan (.3 million) since 2017, Shanghai People's Procuratorate announced.
Most of the criminals moved to remote regions or overseas countries as local police cracked down on telecom fraudsters, prosecutors said.
Three criminal networks based in Indonesia illegally obtained more than 3.2 million yuan from 129 people, cheating them. Pudong New Area People's Court jailed 34 members of the network.
Scammers used fake caller IDs and impersonated China Telecom company operators, bank employees, police and prosecutors, telling the victims their information was leaked and illegally used for criminal activities and asking them to transfer money to a so-called "secure account" they offered, court said.
Prosecutors also pointed to debt-trap scams as a major problem.
Some 118 people in 42 cases have been jailed in 42 cases since 2017. They are convicted of extortion, illegal imprisonment and creating false lawsuits, all common ways used by debtors to force victims to repay "non-existent" debts.