The company has called on all mobile phone operators to follow Vodafone's lead in ending roaming charges altogether.
Broadband Expert commercial director Rob Webber said that mobile phone users are still getting a raw deal, and gave the example of downloading an episode of EastEnders while abroad, but within the EU, which he said could cost anywhere from £65 to £1,600, depending on mobile broadband provider.
The cost of downloading an episode of EastEnders (around 320MB) on BBC iPlayer if the subscriber is outside the EU would cost £2,400 with T-Mobile and £194.87 with Vodafone.
The chart below, created by Broadband Expert, shows the large discrepancies between the major providers for downloading data abroad.
* Based on £4.99 for 25MB per day in the EU and £14.99 for 25Mb outside the EU
** £3.00 in Australia, Cyprus North, India, Israel, Japan, Mexico, Philippines, South Africa, Taiwan, Thailand, Turkey, Puerto Rico, Virgin Islands (USA) and USA, Hong Kong and £6.00 per MB for the rest of the world
*** Based on 320MB per episode
Cotton seedling freezes to death as Chang'e-4 shuts down for the Moon's 14-day lunar night
Fortnite easily out-earns PUBG, Assassin's Creed Odyssey and Red Dead Redemption 2 in 2018
Meteor showers as a service will be visible for about 100 kilometres in all directions
Saturn's rings only formed in the past 100 million years, suggests analysis of Cassini space probe data
New findings contradict conventional belief that Saturn's rings were formed along with the planet about 4.5 billion years ago