How do you answer the complaint If you learn how to spell?

The simplest way is to learn to spell. Some find it harder than others. You could always point out that English is the hardest of all Western languages to spell because it is made of Words from many different languages that use different rules of spelling.

The more you use Words correctly spelled (not text-speak) the more automatic your use of correct spelling will become. Practice makes perfect. (And here you can even use the spell checker.)