memory corruption

        void removeNonLetters(char* phrase) {
            int ascii = 0;
            int i = 0;
            while (*(phrase+i+1) != '\0') {
                i++;
                ascii = (int)*(phrase+i);
                if (!((ascii > 64 && ascii < 91) || (ascii > 96 && ascii < 123))) {
                    int j = i;
                    i --;
                    while (*(phrase+j) != '\0') {
                        j++;
                        *(phrase+j-1) = *(phrase+j);
                    }
                }
            }
        }