Telstra has refunded more than 72,000 customers more than $9.3 million after they unwittingly subscribed to an ongoing service from a third party supplier.

Key points: Customers were signed up to the Premium Direct Billing program without realising it

Customers were signed up to the Premium Direct Billing program without realising it There were cases where children accidentally signed up their parents' accounts

There were cases where children accidentally signed up their parents' accounts The ACCC believes there are more customers owed compensation

The Premium Direct Billing (PDB) program saw customers signed up without even realising it when they used third party apps on their phones.

Australian Competition and Consumer Commission (ACCC) chairman Rod Sims said it was too easy for people to unknowingly subscribe.

"Really you didn't have to do much to sign up," Mr Sims said.

"You didn't have to put in your credit card details, you didn't have to double-click anything."

The ACCC said for some time Telstra received more than 10,000 complaints a month from disgruntled customers who were paying for a service they did not want.

In April this year, the Federal Court fined the telco $10 million for making false or misleading representations about charges for digital content, such as games, wallpapers and ringtones.

It also put in place a redress program for affected customers which has resulted in the payout to customers.

But the ACCC believes there are many more customers who are owed compensation.

"There's more people who should be contacting Telstra seeking a refund," Mr Sims said.

"Without realising it there might be another line on that bill which is a subscription which could be $10, $20, $30 a month which you have been taken to sign up for even thought you never knew you did."

The consumer watchdog said there were many incidents involving children accidently signing up their parents' accounts to the PDB service.

It said once customers were signed up, even if they realised the mistake, it was very difficult to unsubscribe.

"It really was extremely bad behaviour," Mr Sims said.

"The good news is Telstra is being very proactive in giving people refunds."

Customers who think they may be impacted should contact Telstra.