Buying a phone directly from the manufacturer is the best way to ensure you won’t be locked to any particular network and can easily use your phone almost anywhere in the world. Neither Samsung, Apple, Huawei, or any other major manufacturer typically locks their devices to GSM or CDMA networks. Only some mobile carriers tend to do this. But carriers like Verizon offer unlocked phones, meaning you can switch to a different carrier and network if you terminate the contract.