Data does tend to be the last one to work properly.
Check your My o2 to see if you paid the correct amount - if you did, keep rebooting your phone and if it's still not working then contact o2 on social media; If you message O2 on Facebook (https://o2uk.co/O2CFB) , Twitter (https://o2uk.co/O2CTW) or Instagram (https://o2uk.co/O2CIG) , they should be able to help you with this.
If you didn't, then pay the outstanding balance and then follow the above.
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 Do not publish personal details (email, phone number, bank account).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