There are a couple of reasons why this might be @Kirk76 but the important 2 are what does his/your My o2 say he should be paying and where did you sign up to the deal?
If My o2 has a different tariff/air time price then you need to get in touch with who you ordered from.
It might also be a pro rata charge (for a part month to get you in the billing cycle - explained in the quote below from https://www.o2.co.uk/help/account-and-billing/your-bill
You’ll get your first bill within four days of joining O2, and you’ll be charged 14 days after you receive it. Your official billing date is usually the date you joined us, and it will be the same every month.
If you joined us on the 29th, 30th or 31st of the month, your official billing date will be the 1st of the following month. Your first bill will be pro rata, which means that we’ll charge you for one full month’s airtime, as well as any airtime you use in those first few days before your billing cycle starts.
If you’ve upgraded your device, your billing date will stay the same.
Your next bill will be pro rata and might include a charge from your old tariff or Airtime Plan. If you're on O2 Refresh we split your bill in two, so you’ll see two payments each month:
Otherwise, see if any of the links below help:
Guide: Where is my discount or Extra Data?
Guide: How do I get to the 'Download Bill' page?
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 Do not publish personal details (email, phone number, bank account).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
