The fraudsters, largely from Poland, have made off with almost four million francs ($4.5 million) in reported cases so far this year, German-language television broadcaster SRF reported on Tuesday night, citing federal police information.
At least 837 victims have been defrauded of money by pretend grandsons or friends, up from a total of 369 in 2013, the 10vor10 public affairs programme said.
On average, the victim handed 52,782 francs to people colluding with the scammers as “messengers”, the programme said.
Typically, such criminals use phone books to seek out people with “older sounding” first names.
They make hundreds of calls to find their prey, pretending to be the young relative or friend of whoever answers.
The fraudsters use questions like, “Guess who’s on the phone” or “Do you know me?” to entrap elderly people.
In the majority of cases, the callers phone from Poland, according to federal police.
In Switzerland, they have accomplices who act as “mules” to collect the money.
Typically the phone call starts off with cordial conversation but then turns to an urgent plea for money, 10vor10 said.
The caller, speaking in good German, makes up a story about how he cannot come to personally pick up the money but will send a “lawyer” or “friend” to do so.
In some cases, the victims give jewellery and other valuables in lieu of money, SRF reported.
The calls are mostly made from abroad with anonymous prepaid mobile phones, making it difficult for police to track down offenders.
However, investigators in Switzerland, Austria and Germany say the vast majority of these fraud cases involve the same offenders, with an extended Polish-German Roma family network a prime suspect.
This clan, with several hundred members, was earlier implicated in a scam to sell worthless carpets as expensive Oriental originals, RTS said.