You need to have sharer plans on the phones that you want to share data with.
You are capable of sharing, but it's not setup to do so yet.
Your partner needs to change to a share plan tariff.
This means you need to call customer service or check if they can change their tariff in their MyO2 http://www.o2.co.uk/myo2
The shared phones need their own specific contracts to enable sharing.
Guide here Guide: How to Share Data on O2
You need to call O2
You can use Skype to call.
All numbers including Skype are in this guide
Advice from an O2 Guru regarding a way to get through:
When you call, you will be asked for the reason you are calling,
Stay silent for 15 seconds and you will be taken to the keypad options.
Press 2 for Everything Else
Press 5 for More Options
Press 7 for Anything Else which will put you though to an advisor.
Press Upgrade, Lost/Stolen or Fraud if you have to.
8am is the best time to call
Please read the guide.
They need to be specific shared data contracts.
All detals and prices in the guide.