Unlock Used iPhone 6s Plus
So, I am trying to unlock an AT&T iPhone that I purchased off of eBay, but it keeps saying "Looks like the IMEI number you entered doesn’t match an AT&T device." even though I'm sure it is an AT&T device because I can't use it with any other carrier. I don't think it is blacklisted or have any issues because I was able to use the phone with H2O wireless perfectly fine for over a year. Other answers say that I should be on the AT&T plan for at least 6 months, but I don't want to spend extra on getting an AT&T plan again. Any help is appreciated!