See text above, if it says it is unlocked then Unlocked phones can be activated with any gsm service for calls and text messages, often times to get internet data and picture messages (mms) you have to set up apn settings that are specific to your carrier. You do not need to set up any settings for original carrier, everything will work out of the box. To get apn settings for your carrier please contact your carrier or search online. If it says specific carrier then it can only be activated with those carriers.
Do not assume that it will work with your carrier unless stated. The item "Samsung Galaxy S8 G950U Unlocked AT&T T-Mobile Boost Cricket Verizon SHADOW LCD" is in sale since Thursday, January 17, 2019. This item is in the category "Cell Phones & Accessories\Cell Phones & Smartphones". The seller is "mobileitems" and is located in Deerfield, Illinois. This item can be shipped to United States, Canada, United Kingdom, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Australia, Cyprus, Slovenia, Sweden, South Korea, Taiwan, South africa, Belgium, Ireland, Netherlands, Poland, Germany, Austria, Bahamas, Israel, Mexico, New Zealand, Singapore, Switzerland, Norway, United arab emirates, Qatar, Kuwait, Bahrain, Croatia, Antigua and barbuda, Aruba, Belize, Dominica, Grenada, Saint kitts and nevis, Saint lucia, Montserrat, Turks and caicos islands, Barbados, Bermuda, Brunei darussalam, Bolivia, French guiana, Guernsey, Gibraltar, Guadeloupe, Iceland, Jersey, Jordan, Cambodia, Cayman islands, Liechtenstein, Sri lanka, Luxembourg, Monaco, Macao, Martinique, Maldives, Oman, Pakistan, Paraguay, Reunion, Uruguay.