"What is changing?
You will see a 2.7% increase to your monthly plan charge on any bills you receive from the 28th May, if you joined or upgraded to a 12, 18 or 24 month Pay Monthly or Small Business contract before the 23rd January 2014. This increase is in line with the Retail Price Index (a measure of inflation) published by the Office for National Statistics on the 25th March 2014.
If you joined or upgraded after the 23rd January 2014 then you are not affected by the price increase. If you have upgraded to a new contract in the last 30 days you may still receive a letter, however the price increase is not applicable to your new plan.
"For some customers, we are also making changes to a number of other charges such as standard UK calls and texts when you go over your mobile allowance, and other services like calls to 08 numbers, international calls and MMS. These changes will take effect from the 28th May."
http://terms.ee.co.uk/ee-price-changes-information.html