hi is the personalization not avaible instore for iphones

I just asked my brother to get me an iPhone XS as he was in Florida and I had read that you can have your iPhone XS customised for free with an engraving on the back panel. But the sale person did not offer that and he got it without it. I saw online that the Florida Mall is one of the listed places. My question is. Is this only for online deal and can it not be done at the store purchase also. Kindly let me know. Thanks regards