Can I use an unlocked Helio phone with my T-Mobile service?
No. Helio’s phones and network are CDMA, which doesn’t use sim cards, and also cannot be unlocked. T-Mobile’s phones and network are GSM, which requires sim cards in order to work. They are two completely different technologies and are not compatible with each other. Unlocked only refers to GSM and iDEN phones and means they can be used with a sim card from any compatible provider.