We report on the replacement of E3E4 (Crack) and refurbishment of Minimum Bias Trigger Scintillator (MBTS) counters as part of phase I upgrade for the ATLAS experiment at the European Organization for Nuclear Research. Crack and MBTS counters, located between the central and extended Tile Calorimeter barrels, are used for correcting the electromagnetic and hadronic energy responses, respectively. They are situated in close proximity to the beam axis of the detector. During Run 2 (2015-2018) data taking period of the LHC energy √s = 13 TeV, Crack and MBTS scintillators were severely degraded by radiation and had to be replaced. The phase I upgrade has commenced since the beginning of LHC long shutdown 2. The upgrade activities which were finalized with a strong contribution from South Africa comprised the assembly of Crack and MBTS counters, their qualification and characterization using radioactive sources (Sr90 and Cs137) and their installation on the ATLAS detector. The University of the Witwatersrand was previously involved in the radiation qualification and selection of the scintillator material to be used in the counter production.