I bought my I phone 8 straight from apple online since 2019 I would like for my phone to be unlocked with other carriers

If you bought it directly from Apple it should already be unlocked unless you bought it through a carrier specific installment plan.

If it isn't unlocked, only the carrier it is locked to can unlock it.

You verify lock status in Settings->General->About->Carrier Lock

It can be done but only your carrier can unlock the phone. Read about it in Apple Support here:

How to unlock your iPhone for use with a different carrier - Apple Support

Apple does not control this. Only the carrier can unlock the phone.

Your first step....... contact your current carrier to ask them to unlock the phone. Please note that they are under no obligation to do this though, so they may or may not be able to help you.

If your carrier will not unlock the phone for you, you will have to keep using their service. Or, if you want to use another carrier, you will need a new phone.