Only detects the first element of the array when it's compared with the input. I've tried with a lot of things and it's doesn't work out

Question

It was supposed to be a function that detects when it's a vowel. But, it didn't work out as expected

#include <stdio.h>
#include <conio.h>

// It didn't work out. It failed

// It was supposed to be a function that detects when it's a vowel.
// But, it didn't work out as expected

int isVowel(char c) {
    char letters[] = {'A', 'I', 'U', 'E', 'O', 'a', 'i', 'u', 'e', 'o'};
    for (int i = 0; i <= 9; i++) /* It detects A, but nothing else*/ {
        if (letters[i] == c)
            return printf("A vowel\n");
        else 
            return printf("Not a vowel \n");
    }

}

int main() {
    char c;
    printf("Press a key: ");
    do {
        c = getch();
        char ans = isVowel(c);
    } while(c != 13);
}

Any way I can fix it up to compare the whole array?