the best is the call the helpline and clarify this problem. if you dont want to waste your time, like what one of the replies is that, you can actually do it online.

your miss call alerts only work when your phone is out of coverage, or turned off. other than that it will not work.

please correct me if i am wrong

they do apparently. i kena twice last year. not worth it le having the voice mail unless we are some kinda VIP. instead, i turn on my call waiting service

so the best is to call the helpline. i think we can activate the miss call alert via OCS right?

so go ahead with it. it;s good to have that feature turned on because you never know when you have multiple miss calls when you aren't with you phone or when you are out of coverage