As frustration mounts with cellular service contracts, early termination fees, and high overage charges, many people are turning to pre-paid mobile services. Yet, often these services have a limited selection of phones. We wondered if the pre-paid phone and service was worthwhile. So, today we looked at the both the hardware and the service for the Samsung M340, as offered by the Common Cents Mobile carrier. This phone is also known as the Samsung Mantra and is available from several other mobile carriers.