Can someone here tell me if the Verizon iPhone X will still be able to be used with a sim from AT&T or T-Mobile even if it has a Verizon line of service in it? -OR- does that Verizon line of service in the phone need to be cancelled out before it will work? does the phone have something that allows you to select the service you want to use like for example the service already on the phone or the sim card that may be in the phone?