Let's get some terms straight:
Unlock - take a device that is tied to a network and make it usable on other networks. This has to be done by the original network
Jailbreak - a term used for iPhones that is equivalent to rooting an Android device
Which is what you want to do? Be aware - a Verizon Galaxy S5 may have VERY limited ability to connect to carrier networks other than Verizon, there was a distinct model number for Verizon and Sprint compared to AT&T and T-Mobile.
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