Why do you think you are being overcharged @Antec ?
As advised above, check what the bill is showing as it might be one of the sims has been subscribed to something you don't want, or has an extra that was free but is now paid for.
Some useful guides are below:
To check what is on the bill: Guide: How do I get to the 'Download Bill' page?
If you prefer using the My o2 app: Guide: My O2 App
If a premium rate service is showing: Guide: Have you fallen for or been conned into a premium rate scam? What to do next
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 Do not publish personal details (email, phone number, bank account).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
