Phones 4U and Carphone Warehouse have sacked a number of staff in a clampdown on mis-selling.
Both retailers have monitored sales and investigated staff in recent weeks for implausibly high transactions, resulting in high bonus payments, given the current retail climate.
In February, all staff in a Swindon Phones 4U store were sacked for sales to box breakers.
A number of Phones 4U staff in Gloucester and Bath have also been suspended for suspected gross misconduct.
In some cases, Phones 4U staff are alleged to have sold up to six prepay handsets twice per day to box breakers, entering a different name to each sale to avoid detection.
Carphone has also acted to stamp out box breaking.
In November, it dismissed all staff in its Eltham outlet. Three staff were sacked from a Southwark branch in January also, and further staff have been suspended.
Carphone is sending out ‘loss prevention’ officers into certain stores to check selling patterns and CCTV footage, claimed staff.
In some cases, they are contacting customers to validate sales.
Staff claimed extreme sales targets were forcing their hands. Both retailers denied targets were too high.
A Phones 4U spokesperson said: “We have never tolerated box breaking and never will.
“We’ve always made it explicit that if we detect this type of activity in stores, we will not hesitate to take action and discipline those involved. We continually review and adjust our sales targets to ensure they’re achievable and in line with demand.”
A Carphone spokesperson said: “We are confident that our systems and processes which are in place minimise the possibility of box breaking.”
Meanwhile, Phones 4U store managers will be disciplined if they continue to under perform, staff were told at monthly briefings last week.
Store managers at its 80 worst-performing stores each month will meet with area sales directors to explain.
Store managers were told the bottom four stores in every region will be