WHY does ‘X’ Autocorrect to ‘C’ or ‘Z’

I type ‘X’ and it auto corrects to ‘C’

Why? Is there a setting to change this even through I don’t think I should have to. When an automated appointment text comes through and I type ‘X’’ to cancel and a ‘C’ to confirm populates, it’s really frustrating. This “smart” phone should know. better than to change single letters especially when this auto correction has costing me money. (Late cancel fees.) What does Apple done to resolve this?