I am using iPhone 17 Pro, ONE NZ on an eSIM.

Last Friday I updated my phone to iOS 26.4 and since then my mobile data stopped working.

Phone calls and text messages work fine, wifi is good as well, but only mobile data.

My mobile plan is a total unlimited, no usage limits, no speed limits on it.

I don't think this is my phone's physical hardware issue, because I have another eSIM on my phone, which is under Spark NZ, and it works perfectly fine.

I tried rebooting the phone, force rebooting, resetting the network settings, resetting all the settings, updating carrier settings manually, and resetting APN details.

But none of above worked for me, and I visited my local branch of ONE NZ on Sunday but they couldn't find out what is going on with my phone.

I reached out to Apple as well, a friendly senior technician tried to help me out and in the end of the couple hours of phone conversation with him, he eventually suggested me to erase all data on my phone and set it up from the scratch. (which I don't want to do and don't think will help solving this issue)

Yesterday I tried transferring my eSIM to my GF's phone to see what happens and guess what, the mobile data worked! But it still didn't work when I transferred it back to my phone.

A staff at the local ONE NZ branch said he raised a ticket to the head office and they will figure out what is happening with my phone, which will take a few days ... my phone was bought overseas(in USA), it might be something but I don't believe so as it has been working totally fine since purchase(last October) until now.

Anyone has a clue what might be going on with my phone and what can I do to solve this issue? Or has anyone had a similar issue with their phone after getting an update?