Like Vodafone, Optus has started to receive complaints about iPhone billing problems relating to excess data charges.

Yesterday Vodafone revealed a number of customers had been hit with larger than expected bills after the carrier had not correctly transitioned them onto a new plan when they purchased an Apple iPhone.

Today one Optus customer told ZDNet.com.au that he had received a $693 bill with large data excess charges, despite the fact that he was on a $79 monthly iPhone plan with a 700MB allowance per month, of which he had used under 100MB.

The customer called the Optus call centre, where the operator tried to explain the extra charges away with pro-rata data limits. The theory was that because he had only been billed for part of the month he only had a portion of his 700MB allowance.

However, the bill covered around two thirds of the month, which meant that the under 100MB usage the customer had clocked up would have been within the allowed data usage.

After a second call, Optus discovered that he was still on his previous GPRS data plan, having not been correctly migrated, although the voice plan had been. His bill was reduced to just under $90.

However almost $130 was charged to his bank account when the time came to pay, which he has not yet sorted out. The customer speculated that with the bedlam on the day of signing up, human error could have caused him to have not been migrated to the correct data plan.

Optus declined to comment on how widespread the issue was.