Enter the main menu of your Windows Phone.
Hit the arrow icon to see all options.
Go to "Settings" icon nut.
Enter the "keyboard" submenu.
Then click "Write Settings".
There you will have selected a language, in this case, "Spanish", click on it.
Disables the "Fix misspelled words" option.
From here you can also change other parameters writing as "Suggest text and highlight misspelled words" or "Capitalize the first letter of a sentence."