When people are speaking, they almost never misspell anything they say -- they aren't spelling it at all.
When you, the writer, report as dialog the speech of your characters, why would you want to insert misspellings for them?
The only excuse is to indicate a non-standard pronunciation. And trying to use spelling to show pronunciation is a much-discussed topic on this board, with the overall conclusion being that it's a bad idea for a large number of reasons. (For example, the way English-readers interpret spelling into sounds is based on their own individual background & education, and you have no way to control how any reader will "hear" something you deliberately misspelled -- odds are, their version and yours are not the same.)
Short answer -- don't get creative with spelling even in dialog unless you have a really really good reason and master-level writing skills. Which most of us don't.