Vodafone is delaying the reintroduction of roaming charges in Europe by three weeks.
The phone network had planned to bring in post-Brexit roaming fees on 6 January, matching other networks who plan to do so in 2022.
But it said more time was needed for testing, and the change will now come in at the end of January.
EE has also delayed resuming its roaming charges, which were planned for January, until March.
Before the UK left the EU, users were able to use their calls, texts, and data allowance in their mobile plans in any EU country. But the EU trade deal of December 2020 gave mobile operators the option of reintroducing charges.
The Three network has also said it will bring in roaming charges between the UK and Europe, though their change is planned for May 2022.
That means that of the largest mobile networks, only O2 has not announced any plans for the reintroduction of roaming fees.
Explaining the reason for delaying its planned changes, Vodafone said it was not ready to bring in the new system.
"We have pushed back the introduction of roaming charges to the end of January, giving time for further testing to ensure the best possible experience for customers purchasing our £1 per day bundles. Until then, customers will continue to be able to roam without charges."
The £1 a day charge is Vodafone's best price, and only applies when bought in an eight or 15-day bundle. The usual planned price is £2 per day in fees, matching EE and Three's planned pricing.
EE said the shift in its plans was caused by unspecified technical delays.
"Making big changes to billing systems in mobile phone networks is always risky," said Ben Wood, chief analyst at CCS Insight and founder of the Mobile Phone Museum.
"The backlash and negative publicity for any network operator that does not get it right would be immense if a customer ended up with an eye-watering roaming bill.
"My guess is that rather than rushing out a change, the operators are delaying the introduction to be absolutely sure everything is working.
"Given the current Covid situation it's not like lots of people are travelling, so the operators are not going to be massively exposed on unexpected roaming costs."
EE to reintroduce Europe roaming charges
Vodafone to bring back roaming charges from January
Three to bring in Europe roaming charges
Mobile roaming charges: What you need to know
Australia cancels Djokovic visa amid vaccine row
Decisions have consequences, Nadal says of Djokovic
Dozens killed in crackdown on unrest in Kazakhstan
Twists and turns of Djokovic's Australia mess
The messy cost of China's harsh lockdown playbook
Is China luring poorer countries into debt?
What happened to these Capitol rioters?
'A nation in decline' – how the world saw Capitol riot. Video
EU looks for role in Russian row with West
Zuma's South Africa: Scandal, bullying and fear
PinkPantheress wins BBC Sound Of 2022
How more people got a taste for caviar during lockdown
Do you fancy taking up running?
Couch to 5K is a nine-week programme designed for beginners
QAnon and the plot to break reality…
Journey into the dark undergrowth of modern America
© 2022 BBC. The BBC is not responsible for the content of external sites. Read about our approach to external linking.