Sales staff at a Telstra franchise in the Northern Territory would lie about their customers' employment status in order to manipulate the company's credit check system, a former employee has claimed.

The former employee spoke anonymously about the techniques they would use to falsify client information in order to sign them up to contracts and additional services, even when their income was insufficient.

Last month, the ABC revealed Indigenous Australians in some of the nation's most remote communities had been handed exorbitant Telstra phone bills after signing up to contracts they did not understand.

In one case, a Tiwi Islands woman living on Centrelink payments, who signed up to a mobile phone contract to keep in touch with family and friends while having dialysis treatment in Darwin, quickly accrued almost $6,000 in excess data charges.

Following the publication of the story, a former employee, who wished to remain anonymous, spoke to the ABC about the tactics they would use to sell devices and plans to clients.

How credit checks were gamed

The former salesperson said a general lack of understanding about what they were signing up to meant Indigenous people frequently fell victim to the tactics, even though they weren't specifically targeted.

"A lot of the Indigenous people didn't really have a great credit [history], just because they were on Centrelink and stuff like that," the salesperson explained.

"We were told that we needed to forge the credit check or manipulate the system by saying, rather than unemployed, [the customer] was self-employed."

Made-up phone numbers were sometimes entered in the employer contact number field.

At the next step, they claimed they would list clients as having been self-employed for longer than five years, bypassing the need to list a previous employer.

Based on this data, staff were then provided with a credit score of what they were able to sell the client.

Phones could be repaid at a cost of anywhere from $90 to $199 a month, while insurance, accessory bundles and, in some cases, additional devices would drive the monthly bills even higher.

"So basically they'd be walking away with two devices — a phone, a tablet — $360 worth of accessories for the tablet, insurance on both devices, plus the plan," the former employee said.

"At the end of the whole process, when they have to sign the contract, we do go through it, but how far they really understand depends on the customer.

"It was quite often that we'd get people coming in, and then you'd see all over the shop, people walking out with mountains of accessories, phones, devices."

A second employee confirmed these claims but did not wish to speak on the record.

Internal investigation

The former employee claimed customers often returned to the store questioning the large bills they had received, and were turned away.

"It got to the point where we were having so many people coming in with billing issues that we were told by management that 'in-store we do not deal with billing issues— because billing issues do not give us sales'," they said.

The telecommunications giant said it was working to improve practices at the point of sale. ( AAP: Joel Carrett, file photo )

They were instead redirected to a call centre, the employee said.

In late 2017, the number of customers who were not paying their bills was picked up by Telstra's internal monitoring processes.

Once aware of the issue, Telstra undertook an internal investigation that identified, "two store employees were engaging in unusual behaviours consisting of manipulating credit check information".

These individuals are no longer employed at the Telstra franchise and Telstra said its investigation showed the issues were not systemic.

The telco also said it had implemented additional procedures to ensure fair sales practices since the review.

"These include requiring stores to cease creating new customer identification numbers and conducting audits of contracts and sales," the spokesperson said.

Sales commissions questioned

Financial counsellors told the ABC they believed sales commissions could be motivating Telstra staff to upsell devices.

The former employee said sales commissions motivated these practices and some pressure to game the credit check system came from management, a claim denied by Telstra.

"The Telstra licensee refutes the claims undeniably and the audit confirmed the behaviour was limited to a few consultants," Telstra said in a statement.

"We have not identified any further occurrences since it has been addressed."

Telstra declined an ABC request to speak directly with the franchisee.

The former employee said they left the franchise of their own accord after becoming uncomfortable with the sales practices.