You can move to another carrier anytime you want. They will all buy out your current service immediately.
In the past, there were competing wireless standards which caused the device makers to build different models for each carrier. Today, the global standard is 4G LTE and there are about 23 different frequency bands. Previously, device manufacturers would offer "North American" models, "Asian" models, "Middle Eastern" models etc. Each had specific frequencies and very often, added "bloatware" specific to the carrier. Until Apple came along, it was the carriers that told the device makers what they wanted and didn't want included. I remember Cingular Wireless having NOKIA build them an E-62 model because Nokia's E-61 model had wifi dialing, SIP calling, and text-to-voice conversion, all features that were intentionally removed at Cingular's request on the Nokia E-62, a model bastardized specifically for them.
Thanks to Apple for deciding to simplify things and build one model that will work for any carrier, anywhere. From the iPhone 6 forward, you can now move your SmartPhone from one carrier to another, without even having to reset anything or losing any of the current content. In fact, if you have a Verizon iPhone, or purchased one from Apple, they're already unlocked. If your device was purchased from an AT&T, Sprint, or T-Mobile store, it is locked to those carriers, until the device is fully paid off.
Remember in the old days where all of your contacts and SMS messages were stored on your SIM card? Not any more! Today, it's only carrier settings. That means changing the SIM card only changes the carrier setting information, not any of your other personally stored content on the device.
Whether you plan on moving to another carrier or not, you should immediately contact your carrier once your device is payed for. By law, they must unlock the device once it's paid for. Unlocking it will not effect the performance of the device with the current carrier. What it will do is increase the resale value by at least $50, as once it's unlocked, it can now also work on any other carriers network. Often times, when requesting an unlock, the carrier may mention off sheet retention programs thinking you are getting ready to bust a move to another carrier.
Dr Wireless specializes in seamlessly moving business and enterprise accounts from carrier-to-carrier with absolutely no downtime or inconvenience. Since we are business solution partners with all of them, it's very simple for us to orchestrate moving lines between each. For more information, please contact us.
Joel Saltzman has over twenty years of wireless industry experience. He is currently CEO and Chief Wireless Analyst for Dr Wireless.