As the company could not be contacted, iTWire asked Telstra if it could offer comment on the incident.
A Telstra spokesperson said in response: "The company is a Telstra dealer who supports Telstra products and specialist business requirements for some of our enterprise and mid-Market customers.
"We’ve been in contact with the dealer and have been told some 'high-level' Telstra business customer information, such as mobile phone numbers, may have been accessed from its order fulfilment system.
"Our specialist cyber security team is working closely with the dealer to help them resolve the issue.
"We employ strict guidelines for how our partners access and store customer data. No Telstra systems were breached as part of this attack."
The gang behind the Avaddon ransomware claims on its website that the company did not want "to co-operate with us, so we give them 240 hours to communicate and co-operate with us. If this does not happen before the time counter expires, we will leak valuable company documents."
As of this writing, the so-called time counter is set at four days and 15 hours.
The Avaddon gang claims to have a big amount of data on mobile devices, tens of thousands of SIM cards and information for them: "financial information, contracts, banking information and much more".
The gang has also threatened to launch a distributed denial-of-service attack on Schepisi and reminded the company that encrypted data could only be decrypted with the gang's own tool.