o2 have no way to track when the sim is delivered to you @Joelam , so they charge from when it is despatched.
If you contact customer services and politely tell them when you received the sim in the post and ask them to refund the monthly charge until then, in most cases they will do so.
Call 202 from the o2 sim, just after 8am and you should get through ok.
Alternatively message on social media:
Click here for O2 Social Media links
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 Do not publish personal details (email, phone number, bank account).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
