http://support.t-mobile.co.uk/help-a...cat=NEW_PRICES

copy pasting the FAQ, just in case

What are the changes and who will be impacted?

From 9 May 2012 we’re changing some of our prices. This means that if you joined or renewed on one of our pay monthly price plans before 1 February 2012, your monthly charge will increase by 3.7%. We know that price rises are never great news, but we’re still committed to giving you the best service and network possible.

The price rise will only affect the amount you pay each month for your plan. All other charges, such as call costs, texts and Boosters that aren’t included in your allowance will stay the same.

Why are T-Mobile introducing these price rises?

Due to rising costs of the business linked to inflation, we’ve had to re-evaluate our prices and introduce a rise from 9 May 2012.

How will this appear on my bill?

Your monthly price plan will be updated to include the 3.7% increase. The new price will show on the bills you receive after 9 May 2012.

Can I cancel my contract because you’re increasing my monthly service charge?

Our pay monthly terms and conditions allow us to increase charges up to the Retail Price Index (RPI) figure in any 12 month period. The increase in your price plan charge is not more than the 3.7% rate of inflation as measured by the RPI in February 2012.

If you still wish to cancel your contract, you’d need to pay any cancellation charges that may apply. You’ll find the details in Clause 7 of our Terms and Conditions.

Who will be impacted?

Consumer and business pay monthly customers who joined T-Mobile prior to 1 February 2012 will see an increase in the cost of their monthly plan by 3.7% from 9 May 2012.

Customers on our latest consumer tariffs such as You Fix, Full Monty, the rest of our current consumer pay monthly tariffs and Mobile Broadband will not be impacted.

Why are some customers affected and not others?

The majority of our customers are affected by this change. However, our latest tariffs such as You Fix, The Full Monty and the rest of our current consumer pay monthly tariffs took our rising costs into account which is why they are not impacted.

What if I have recently upgraded on a new pay monthly tariff like The Full Monty?

If you renewed since February 2012 on one of our latest consumer tariffs such as You Fix, The Full Monty or any of our current pay monthly tariffs, this increase won't apply to you.
So my tariff is increasing by 37p...