RPI: Each year your airtime tariff will be adjusted by the Retail Price Index (RPI) rate of inflation. Find out more at o2.co.uk/prices. New and re-signing O2 Small Biz customers only when bought direct from O2 on a 24 month airtime contract. Quoted monthly offer price is based on paying £0.00 upfront. Offer ends 7 November 2018. Subject to availability. If you return one of the devices during the change of mind period, you must return the other device too.