The telco blamed regulated fee cuts and A bigger outlay on device repayment credits for the fall.
Last year the Australian Competition and Consumer Commission reduced the mobile termination rates from 3.6 cents per minute to 1.7 cents. For SMS, the rates fell from 7.5 cents to 0.03 cents. Optus blamed its 9.3% decline in operating revenue partly on this.
Optus' parent company Singtel saw a 2% drop in operating revenue to S$4.41 billion (about A$4 billion) compared to the corresponding quarter in the previous fiscal year. This was blamed on the fall in Australian mobile termination rates.
Optus said it now had 1.13 million broadband customers, with 192,000 on the NBN. The telco increased its 4G mobile subscriber base to 5.54 million, which comprised 58% of its mobile base.
Optus said it added 153,000 mobile customers in the quarter, bringing total mobile customers to 9.57 million.
Post-paid handset subscribers grew by 90,000 while the pre-paid segment returned to growth this quarter with net additions of 43,000 subscribers.
Optus chief executive Allen Lew said: "Optus is responding to moderating market conditions with an intense focus on innovative products, unique entertainment offers, and a strong network proposition.
“Our network strategy, which is focused on delivering reach, capacity and reliability in both metropolitan and regional areas, is delivering real choice for customers.
"With our continued commitment to investing in regional areas, which has been boosted by the recent Mobile Black Spots Funding announcement, we are expecting to make further network improvements in 2017 and beyond."