Why doesn't my Galaxy S4 want to return to default instead of custom status?

[AC Question]

My Galaxy S4 doesn't want to return to default instead of custom status.

I've been looking on the forums for a while now for a fix for this issue. My phone is a SGH-i337 version from Koodo (Canadian provider), and i'm having the issue where it is saying my phone is modified so I can't install the latest version of software which it WAS before but I've unrooted along time ago (basically the exact moment I rooted it), I even tried to root my phone again for some of the tricks people have posted but the tutorials and things that I went to go use were outdated and I may just be dumb but hard to follow. I don't want to return to a rooted version I just want to update my phone lol. If anyone knows how to fix this problem with ease please let me know.

 

[shel692]

Re: My Galaxy S4 doesn't want to return to default instead of custom status.

This should work for you. But I want to STRESS read it, read it again, and a few more time to make sure you understand, I'm having a lack of faith here since you failed to use the search feature of a forum you posted in,
http://forums.androidcentral.com/sprint-galaxy-s-iii/225977-device-status-modified.html

 

[Nickolais]

Re: My Galaxy S4 doesn't want to return to default instead of custom status.

I actually looked at that and read through it, but the tutorial it leads to is a broken forum I guess and the things below are said to be wrong apparently, so i don't know what to do. I'm just looking for a step by step way to set my phone to completely stock so I can update my android version to the latest D: (I may be blind, but please point out where I can find the tutorial).

 

[Nickolais]

Re: My Galaxy S4 doesn't want to return to default instead of custom status.