Istore Somerset West Mall - POOR service

I went into the iStore in Somerset West Mall to book in my iPhone for a battery replacement; they said all was good to go and to come in tomorrow at 10am. I then proceeded the next day, and after them removing screen protectors, etc., they said the phone was purchased in the USA and they couldn't touch it. I then left, and my phone is still in repair mode, and I can't get hold of them to remove it. Absolutely poor service from them!