Q:

“I capitalised this letter”

How do you say, “I capitalised this letter”?
How would a native English speaker phrase the following sentences?

i wrote it with a lower case letter
i wrote it with a capital letter
i have replaced upper case letter on lower case letter.

By “letter”, I do not mean a letter (e.g. mail), I mean the characters used to make words.

A:

1) I wrote it with a lowercase letter.
2) I wrote it with a capital letter.
3) I replaced the uppercase letter with a lowercase letter.

