Sim not supported Iphone6s plus

ONLY the carrier the device is locked to can unlock it for use on other carriers.

You will have to contact the carrier it's locked to and request an unlock.

Note that in many cases, if you are not a customer of the carrier it's locked to, they will not unlock it.

Whoever the current carrier might be to which the phone is locked will need to unlock the phone. Only the carrier can do this.

They will only do this if you are a current customer in good standing and have met the qualifications for unlocking.

When the phone has been unlocked, then you will be able to contact another carrier to set up service with the phone.