My pixel is not unlocked, that's why asking for unlocking itIs this an unlocked Pixel 6? If it is, carrier settings may be locked by the network. For example, my Pixel 6 uses a Straight Talk SIM backed by Verizon's network here in the United States. With that SIM installed I cannot change any carrier settings.
What the audience really needs is a little bit more detail from you, such as whether it is unlocked and what model you have.