0300 numbers normally work @Tash389 , if you are on a personal contract.
However you mention your "o2 business" which suggests you are not ?
If you are on a business contract then you need to customer services on 8002 to find out why you cannot call the 0300 number.
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 Do not publish personal details (email, phone number, bank account).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
