Iphone 7 plus got carrier locked suddenly after using almost 4 years

ishara_K wrote:

I purchased a iPhone 7plus in 2017 from Sri Lanka (Country) and it was working without any issue with local carriers in the country . Recently (in december, 2021) once I updated the iPhone with the latest software version iOS15, then the device got locked suddenly after the upgrade, then I realized that the device is locked with "US T-Mobile / Sprint (MVNO)" carrier by using a paid service, so I would like to get help on this, I really need to unlock my device asap.

Note : This device worked without any issues with the local carriers from 2017 to 1st of December.

That happens when the phone wasn't properly unlocked from the phone carrier, this is the only method How to unlock your iPhone for use with a different carrier - Apple Support

So when you updated the phone it locked back the to the original phone carrier. Only way to get it to work now is to contact the phone carrier.

Sounds like it was hacked to unlock it from T-Mobile before you bought it and the update to iOS 15 restored that lock.

That's what happens when you hack an iPhone to remove a lock. It can get re-engaged at any time, specially when restoring the iPhone or updating it.

At this point the only options are to either hack it again, we can't help you with is, or contacting T-Mobile and ask them to unlock it. Only they can unlock it officially. See here: link-> How to unlock your iPhone for use with a different carrier - Apple Support

Officially unlocked devices will not ever re-lock to the carrier that unlocked them for any reason.