<select name="webone_sms_gravity_otp_send_method" required style="min-width: 300px;">
    <option value="smart_otp"
        <?php echo is_null($selected_send_method) || $selected_send_method === 'smart_otp' ? 'selected' : ''; ?>
    >
        SmartOTP
    </option>
    <option value="otp"
        <?php echo $selected_send_method === 'otp' ? 'selected' : ''; ?>
    >
        OTP
    </option>
</select>