Apple users across the US and Europe have already complained about "dropped" 3G calls when using the iPhone.
According to the lawsuit: "Apple and AT&T have misrepresented to the public the speed, strength and performance of the 3G-bandwidth network."
Apple is already facing a lawsuit in the US filed by a complainant over poor 3G connection rates.
If there are too many users on the network or if there is poor 3G wireless coverage, the iPhone connects to a slower GPRS or 2.5G network.
When 3's 3G network launched one of Britain's first widespread 3G networks, numerous 3 customers complained the changeover led to calls being dropped.
As operators build out 3G networks and rely less on back-up GPRS coverage, such problems tend to recede.
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