They stand for Retail Price Index and Consumer Price Index respectively and are measurements of inflation that guide price annual increases for network contract bills.
Retail Price Index (RPI).
RPI stands for Retail Price Index and is a measure of inflation published monthly by the Office for National Statistics.
Consumer Price Index (CPI).
CPI stands for Consumer Price Index and is a measure of inflation published monthly by the Office for National Statistics.
How does RPI/CPI affect my network bill?
Each year, your Pay Monthly airtime tariff will be adjusted according to the RPI+ (O2) or Consumer Price Index (Three & Vodafone) rate of inflation. Your bill will be adjusted in April by the rate announced in January (Three & Vodafone) and February (O2) that year plus 3.9%.