The online banner ads, SMS message, press, poster, radio and TV ads, by Bartle Bogle Hegarty, said: "Roaming charges abolished".
The complainants said this wording would lead consumers to mistakenly believe that the charges had been removed permanently.
Vodafone explained the ads promoted its decision to remove roaming charges in 35 European countries between 1 June and 31 August 2009.
It did not consider the word "abolished" to be misleading, as the dictionary definition 'formally put an end to' did not necessarily imply a final termination.
The ASA noted the ads used the term abolished to describe a three-month suspension of roaming charges.
However, it said none of the ads qualified that claim to clarify the intended meaning.
It felt consumers would be led to understand that the charges had been permanently removed.
The regulator concluded that the ads were misleading and told Vodafone to ensure that significant conditions of promotions were made clear in all future advertising and did not contradict the main claim.