Virgin mobile SIM card?

my phone is unlocked, just wondering if changing my sim card my phone will be locked again? cause virgin sent me an email saying they are changing my sim card for free so my phone works better?

just wondering if i have to change it? and what will actually change by doing so

thks :)

Nope, you are fine, once it's unlocked, it's unlocked for good. :)

thks for the reply, and what advantages should i get from changing sim card , or whats the point virgin wanting to change sim card? :)