The only exception and you should ask around are the Apple phones but if you have not paid off the contract the IMEI may be in a database of phones that carriers will not transfer to their network.
If you don't want such limitations, never buy anything but unlocked phones. Virgin and others lock phones and you pay until the end of the contract before it is released.
The very new to this try to "do myself." There are long prior discussions we should not be repeating here.
I have new phones from Virgin Moble, a Samsung Galaxy A6 and Motorola Moto G6 Play. I do not want to have to be limited to use Virgin Mobile. Long story, but I hate and am at war with Virgin Mobile. I plan on selling the phones.
Will they need to be unlocked or are they locked in to Virgin Mobile? Both phones use SIM cards. Both phones are fully paid for and belong to me. If they need to be unlocked is this something I do before selling them or would the buyer(s) need to do that? If I need to unlock them, how do I do that? Is it something I can do myself? Anything else I need to jknow?
Any insight would be greatly appreciated.