Prepad or Prepaid: How To spell?

The word Prepad is misspelled against Prepaid, which is past tense of "Prepay"

Word contains consecutive vowels 'AI' in between alphabets prep & d is misspelled as 'A'
Wrong Spelling: prep-a-d
Correct Spelling: prep-ai-d
Explore spell check of Prepaid to spell without errors.