O2 has revealed it will increase its pay monthly roaming rates in countries outside the European Union.
The costs of making and receiving calls and sending text messages will be altered, but data charges will remain the same, at £6 per megabyte.
In some cases, prices will be subject to rises of up to 140 per cent.
Alterations will vary from zone to zone. People travelling to Morocco, for example, will be charged 85 per cent (69p) more for making calls to the UK, 140 per cent (73p) more for receiving calls and 33 per cent (10p) more for sending text messages.
In contrast, those heading to Hong Kong will experience 33 per cent higher costs for making calls and 86 per cent higher costs for both receiving calls and sending text messages.
It is suspected that the price hikes have come about as a direct result of the European Commission ruling in July that a cap should be placed on roaming charges within the EU. However, O2 says this is not the case and that the increases simply put its prices on a similar level to those of the mobile operator's competitors.
This represents further unwelcome news for the same consumers who suffered O2's network outages earlier this year. The changes will become active on 28 November.
Telecoms rival Virgin Media has also been in the news today, having announced the UK's first converged calling service allowing customers to use landline talk plan minutes on their smartphone.