The telco came under fire in 2015 and 2016 when it decided to reduce data, calls and text inclusions which were offered with particular prepaid products without consulting or telling affected customers first.
In some cases, Optus reduced the benefits that consumers received when they activated or recharged the SIM card provided with the products.
Optus failed to ensure that these changes only applied to customers who purchased the products after the change was introduced. The company has agreed to credit affected customers with an amount of data, calls or texts equivalent to the amount each consumer missed out on.
ACCC Commissioner Sarah Court says customers are always entitled to the benefits advertised.
"Mobile providers must provide the 'value' and benefits they advertise," says Court.
"Optus Prepaid customers who may be entitled to a credit should visit the Optus website or the outlet where they bought the prepaid product."
Affected customers will have their accounts credited where possible, otherwise they can claim a refund.
"Businesses must act swiftly to offer consumer redress and meet their obligations under the Australian Consumer Law or face action from the ACCC," says Court.
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