It could be the April price rise @william68
See more information here RPI - 2024
You can also check by logging into your account to see if there are any additional charges - either Guide: How do I get to the 'Download Bill' page? or Guide: My O2 App should help.
If those do not make it clear then get in touch with customer services - call 202 from your o2 phone or 0344 809 0202 from any other phone or you can use Skype to call 0800 032 1402 ( Guide: A Guide to Skype )
Alternatively use social media:
Please note, this is not customer services and we cannot access your account. Do not publish personal details (email, phone number, bank account).
Link to our guide on how to contact them can be found here
