Vodafone has said excess charges incurred by some of its iPhone 3G customers were the result of a standard billing practice.

Some customers using Vodafone's 3G iPhone have been hit with hundreds of dollars in excess charges due to data billing cycles.

Company spokesman Greg Spears said the problem occurred because data charges were based on rates from pre-existing plans, which terminate at the end of each customer’s billing cycle.

“It is standard practice to transition customers to a new cap at the end of their monthly billing cycle,” Spears said, adding Vodafone waived contract termination fees for customers switching to new iPhone plans.

The company has changed its billing policy and has commissioned a taskforce to reimburse affected customers and prevent further excess charges.

“From July 23, all existing Vodafone customers that have chosen an iPhone 3G cap can immediately begin using the voice and data allowance within their cap,” the company said in a written statement.

“Existing customers that selected a Vodafone iPhone 3G cap prior to July 23 will continue to use their pre-existing plan until the completion of their monthly billing cycle. Vodafone will waive any data charges that would not have been incurred if the customer had been able to use their iPhone 3G cap, with its voice and data allowance, from the outset.”

Spears said 97 percent of Vodafone iPhone customers have kept within data allocations for the 250MB and 500MB caps.