Vodafone has apologised after some of its customers received roaming charges of up to £10,000.
The mobile network firm says that a technical issue has affected some of its customers' data and voice services while roaming abroad.
Vodafone has said that it's working hard to fix this issue as soon as possible, and its customers will not be incorrectly billed.
As a result of the incorrect high fees, some customers have had their service disconnected.
This has left people unable to use basic phone features abroad, including text messages and the ability to receive calls.
Consumers are more reliant than ever on access to the internet in their day-to-day lives, and rightfully expect it.
Which? reached out to Vodafone for clarity on what affected customers should do if their bill isn't automatically corrected, and what steps it will take if the mistaken charges impact anyone's credit rating.
A Vodafone UK spokesperson said: 'We are very sorry that yesterday, some customers could not use data or calling services when roaming abroad. This was due to a technical error, which we have now fixed.
'Any affected customer should restart their phone to ensure that services are resumed. As a result of the issue, some customers are receiving billing messages in error; we are working through these as an urgent priority and removing any errors from customer accounts.
'Customers will not be charged and do not need to worry about contacting us as we are proactively checking accounts and fixing any issues.
'We are looking at the best way to compensate customers and will contact individuals with details as soon as possible. We will proactively be in touch with any customer affected. Customer credit scores will not be impacted.
'However, customers are always welcome to get in touch with us if they have questions or to discuss their account - they can do this online, via the My Vodafone app, on the phone or visiting a local store.'
If you think you've been overcharged, the first step is to take a good look at your phone bill.
Double-check each of the charges, your text and data use, and any calls you might have made, to work out whether there's been a mistake.
If you've checked all these points and still think the bill for your roaming abroad isn't right, contact your mobile network.
Charging you for anything over and above the agreed cap could be a breach of contract.
If the service you've received falls way below the standard you'd expect, you might be entitled to claim a full or partial refund.
If you were affected by the Vodafone technical fault, you can make a consequential loss claim if you can show that you incurred reasonable losses, and that the cause of the technical fault was a failure to provide the service with reasonable care and skill. These losses could include emotional distress.
Some Vodafone customers are already asking the telecommunications provider what it plans to do to compensate disruption to holidays:
The important thing to note is that you can make a consequential loss claim under the Consumer Rights Act if you are doing so as a consumer - for example, if you incurred expenses in order to use internet services for personal reasons.
While you may also have a claim if you suffered losses as a business owner or while working, you wouldn't be able to make this claim under the Consumer Rights Act, as this only applies to consumers.
Check what level of coverage is promised in your contract, and reference this in your claim.