The mother, who wishes to remain anonymous to protect her Year-10 daughter's privacy, said her child was trying to study on the weekend of the blackout on July 15.

"In the meantime my daughter's getting frantic. Most of their classes are online and they said we haven't got any internet since Saturday," the mother said.

Before the net blackout, the mother told her internet service provider to put a $1 cap on her daughter's excess mobile data usage.

"She asked if she could use her phone as [a] hot spot. I gave permission as I knew we had the $1 excess cap in place," the mother said.

The daughter used her mobile phone as an internet hotspot, but little did the family know they were getting charged in $20 blocks every three minutes.

In 48 hours, the daughter had racked up an $841.31 phone bill despite the cap.

The mother called iiNet on Friday, August 4 after receiving the bill to find out why she'd been overcharged.

She was told the cap takes 48 hours to go into effect.

The company refused to waive the bill and instead granted the family more time to pay off the charges.

"They had a four day outage so we couldn't use any service at all and this was our get around while we waited for our service to come back up," the mother said.

"This problem wouldn't have existed if their service had been running. The charges they were doing were just astronomical."

She has referred the bill to the Telecommunications Industry Ombudsman who are currently negotiating with iiNet.

iiNet did not comment on the specific case.

"At iiNet we pride ourselves on award winning customer service and will work with this customer to achieve a satisfactory resolution," a spokesperson said.