threadPoolTaskScheduler is not stopping even the function is done

I'm working on a Spring Boot project. I'm trying to delay a sendSMS() function for 10 seconds. So I'have found ThreadPoolTaskScheduler which looks really helpful because it can handle capacity of API request by adjusting poolsize.

Here is my configuration,

@Configuration
@EnableScheduling
public class ThreadPoolTaskSchedulerConfig{

    @Bean(name = "smsTaskScheduler")
    public ThreadPoolTaskScheduler threadPoolTaskScheduler(){
        ThreadPoolTaskScheduler threadPoolTaskScheduler = new ThreadPoolTaskScheduler();
        threadPoolTaskScheduler.setPoolSize(5);
        threadPoolTaskScheduler.setThreadNamePrefix("ThreadPoolTaskScheduler::");
        return threadPoolTaskScheduler;
    }

    
}

And here is my code that implements it,

@Service
public class SmsSubscriptionService {
    @Autowired
    @Qualifier("smsTaskScheduler")
    private ThreadPoolTaskScheduler threadPoolTaskScheduler;

     public void excuteReq(){
        log.info("---- HELLO FROM excuteReq " + new Date() );

        this.threadPoolTaskScheduler.scheduleWithFixedDelay(
            (new Runnable() {
                public void run(){
                    sendSMS();
                }
            }), 
            10*1000
        );
    }

    public void sendSMS(){
        log.info("---- HELLO FROM sendSMS() " + new Date() );
    }
}

When I call the function excuteReq(), the sendSMS() will keep looping. Did I config something wrong ?

Thanks a lot.