Will flashing my unlocked, unrooted SGH-i537 render it locked?

I have an unlocked AT&T branded Galaxy S4 Active, bought new on Ebay that I'm using on Metro-PCS and it's beginning to feel dated. I understand the risk of bricking your device, but could flashing potentially lock it? I've been reading the firmware thread how to thread and I'm preparing to incrementally flash my device following the posted guide.

Thanks

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