German phone company Deutsche Telekom has switched over some 50,000 public telephone booths to take old deutsche mark coins through August. "We hope that we can persuade people to bring out their old coins," a spokesman told Reuters. "Coin telephones are still useful in this age of mobile phones." The Bundesbank has estimated 7 billion euros ($8.58 billion) worth of mark notes and coins are still in private hands. Notes and coins can still be swapped for euros at Bundesbank branches and German shops occasionally run promotions allowing shoppers to use the old currency. But the Telekom promotion will offer Germans particular motivation to clean out their piggybanks. Software in pay phones has been reconfigured to allow them to accept 10 and 50 pfennig pieces, as well as one, two and five-mark coins, which were officially phased out after the introduction of euro coins and notes in 2002. But a one-to-one exchange rate means those using the old coins will get their calls at half price. Telekom's decision comes at a time when a growing number of Germans are blaming the euro for the country's economic woes, making them nostalgic for the deutsche mark.