U-Fix, which is hailed by analysts as a first for the UK mobile industry, is a mix of pre-pay and contract tariffs.
The initiative, which is the first time that T-Mobile has targeted the teen market, will enable users to set the amount of money they want to spend each month at either 拢15 or 拢25.
The advertising, which is the operator's biggest activity of the year, will be backed by a multimillion-pound drive, including TV executions by Saatchi & Saatchi, as well as outdoor and print ads.
As the activity is aimed at 16- to 24-year-olds, the ads will be slightly risque and markedly different from the operator's traditional brand advertising.
Karen Harrison, head of brand and marketing at T-Mobile UK, said U-Fix was intended to put 'customers back in control'. Those signing up for the service will be offered a choice of free handsets and 1000 free texts to be used in the first three months.
The launch of U-Fix is the latest attempt by a mobile operator to offer a point of difference in an increasingly competitive market.
Last month, O2 unveiled plans to re-establish itself as a customer-focused business, to increase loyalty among its 14.2m UK customers. Meanwhile, Orange is planning a series of customer-focused offers in the next 18 months.