According to the City of London Police, 11 people were arrested on Wednesday of this week, with police confiscating an assortment of mobile phones, including Apple iPhone handsets and SIM cards.
Also collated into the police evidence bags were large numbers of bank payment cards and passports, which appear to have been used in applications for contract mobile phones and accounts.
The fraud appears to have been carried out on two levels. After obtaining the accounts, the cellphone SIM cards were inserted into auto-diallers that repeatedly dialled international premium rate numbers, so generating revenue for the criminal gang.
The handsets, meanwhile, were sold on to make a further profit for the fraudsters.
According to the BBC, Telefonica's O2 UK operation called in the police after losing around £1.2 million to the fraudsters during July and, after a month-long investigation, the police decided to move in and arrest the suspected criminals.
The BBC says that police officers recovered around £15 000 worth of handsets and hundreds of SIM cards, which indicates the scale of the fraud, Infosecurity notes.
According to the City of London Police, the 11 arrests earlier this week have resulted in six people being charged with suspected telephone fraud that defrauded O2 and other UK cellos of more than £4.5 million.
Police say their investigations involved monitoring addresses in London, Essex, the West Midlands and the North East.
Five people are charged with conspiracy to defraud and conspiracy to remove criminal property worth £4.5 million. A sixth person is charged with money laundering and possession of articles for use in fraud.
All six were due to appear today at the City of London Magistrates Court and a further three men remain on police bail. The remaining two men arrested on Wednesday are to be interviewed today, say police.