You can only use each code twice now.
Once for a refresh contract and once for a MBB contract.
You may be able to apply for more codes off the other numbers though.
http://community.o2.co.uk/t5/Other-Products-Services/O2-Open-and-Friends-and-Family-Discount-Schemes...
I have no affiliation whatsoever with O2 or any subsidiary companies. Comments posted are entirely of my own opinion.
This is not Customer Service so we are unable to help with account specific issues.Currently using:
Pixel 7a (O2 & Lyca), One Plus 6 (Sfr), iPhone 12 Pro Max (Vodafone)