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.