With every possible way if i use "I" word like "NINE" or "FIVE" it's not acceptable. Am i making mistake somewhere?
It is a bug. It took me some time to figure out but if you are using your regional settings that are different than English, this happens. Please switch your lang-locale settings to English. Requires rebooting your phone but works.
Correction: maybe not for all languages but assuming the ones with characters such as the dotless lower-case "i" like in Turkish in their alphabets.