It acknowledges that in a fringe 3G area it can take some seconds to hand over between networks but says this isn't completely controlled by the card because the network will assist in providing the best service possible, based on load and coverage among other things.

It says customers on a data plan should be charged the same amount to access information regardless of whether they are using 3G or GPRS services. Grover says Vodafone had admitted there was a billing problem and had given Food and Commodity Brokers significant credits to offset the charges.

With regard to its help desk, Vodafone says 90 percent of calls about technical issues are answered by technical staff but it doesn't have an unlimited number of such staff.

It is reviewing resourcing of these more complex solutions, a spokesman says.