Europe’s largest telecoms carrier recently disappointed the markets and analysts after posting weak second quarter results and slashing its earnings forecasts for the year, amid fierce competition in its domestic market in Germany.

DT fully realizes that it must expand outside Germany, especially in light of its hemorrhaging of fixed-line customers. In line with this, its investment fund, T-Online Venture Fund, has made a 10% investment in Zug, Switzerland-based Firstgate Holding AG.

Firstgate owns the internet payment service Click&Buy, which allows online retailers to outsource their billing requirements for services, content and goods. The system handles billing in various currencies and the processing of credit cards, direct debits, and the 40 most commonly used payment procedures in Europe.

Click&Buy is used by many brand names to bill their customers. Indeed it used by more than 6,000 content providers across Europe including Apple iTunes, Electronic Arts, T-Online Gamesload, Skype, Nero, Tiscali, Playboy, Financial Times Deutschland, and bild.de among others.

Firstgate says that more than 6 million end customers pay for their internet purchases using Click&Buy. In the UK, its official partner is BT Group Plc, and Click&Buy is soon to expand into South America.

DT already uses Click&Buy, but this deal will allow the German carrier to expand its products and services into more foreign markets. The Bonn, Germany-based carrier did not reveal how much it paid for the 10% stake, but did say that Click&Buy would be integrated with T-Pay, the online payment system of its T-Com unit.

We are convinced that Telekom’s offerings can be marketed even more attractively with the help of Click&Buy, said Jens Becker, of the Finance Board of Directors of the T-Online business unit.

Click&Buy’s leading position in Europe will be of critical importance, particularly in our international online expansion, he added. The broadband boom and consumer enthusiasm for music downloads and games will further accelerate growth.