T-mobile one s system update

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http://forum.xda-developers.com – I have rooted T-Mobile phone, original software that came with the phone at the release date, system update is recently downloaded OTA but not installed. Two or three T-Mobile minor APP were removed using Titanium backup. Understanding that three is probably multiple updates since release date, and I will be loosing root: I am trying to achieve good wifi calls and free tethering. How do I go about to update the phone to the latest software (not interested in custom ROM): can I just install the update? Is there a specific post or guidance for this situation? really appreciate al (HowTos)