Michael Moore, 40, and Sarah Jo Fisher, 33, both of Washington Avenue in Wombwell, had their phones seized by police which revealed 21 exchanges between them and lynchpins in the drug organisation.
The gang, whose members were based in Barnsley, Sheffield and Rotherham, supplied 176kg of cocaine and 18kg of heroin, yielding a total of £6.4m between March and June 2020.
Moore and Fisher were given 20-month prison terms alongside ringleaders Adrees Rehman, 27, Torick Akram, 38, and 36-year-old Imran Mohammed - who were collectively jailed for 34 years - and fellow couriers Joshua Walshaw, 26, and Christopher Lait, 38, who received lesser sentences after the trial at Leeds Crown Court last Friday.
The investigation began in May 2020 when intelligence was received that the gang were operating a nationwide, multi-million trafficking network using encrypted phones.
Akram was the first man to be arrested as he went to work, and a subsequent search of his car recovered two suitcases which contained £1.1m in cash.
A month later surveillance led police to Walshaw’s vehicle - travelling back to South Yorkshire on the M1 at Barnsley - and found him in possession of £150,000 in cash.
This, according to prosecutors, led to Rehman and Mohammed being identified as the lynchpins of the organisation, and subsequently other couriers were found.
Detective Inspector Mick Ryan said: “The scale of drug trafficking and money laundering by this organised crime group was significant, and bringing them to justice involved a tremendous effort from my team.
“We welcome the convictions and the sentences that have been handed down, which takes account of their guilty pleas.
“Drugs have a detrimental effect on society as it fuels crime and destroys the lives of those who take them.
“This gang did not care as they trafficked drugs wholesale, and they wrongly believed using encrypted phones would help them avoid being caught.
“Our team were quick to intercept the operation and arrest them.( “Work has already commenced to forfeit the recovered cash and ensure that those convicted do not benefit from crime as we take steps to recover their assets.”
Efforts to combat organised crime in Barnsley have also been put on the agenda for an upcoming county-wide meeting.
Next month’s South Yorkshire Police public accountability board meeting, on April 11, will see Barnsley officers update other forces on what they are doing to combat so-called county lines criminality, when illegal drugs are transported from one area to another, often across police boundaries.
South Yorkshire Police and Crime Commissioner Dr Alan Billings said: “Spring 2020 was very different from spring 2019 and could not have been predicted.
“There has been a considerable focus on drug offending and those who blight communities by bringing drugs onto the streets.
“As a result of these efforts criminals have been removed from the streets, their assets have been seized and we have been able to put some of that money directly back into the community via my grants scheme.
“We know that drug-related crime has a marked and, at times, devastating impact on our local communities and I hope the public is reassured by the action taken to disrupt the activities of those who would seek to commit this crime.”