As a big/huge telco company, seems this issue is never ending.
Supposedly there should be a TAC request for any kind of subscriptions.

But instead, we were charged directly without us knowing/aware it in the first place until we received these 'unauthorized subscription' SMS or after checking the bills.

And the standard answer was 'you must have surf a website and clicked a link, that's why you have been subscribed and charged'.
When asked how is this possible, where's the log of these subscription transaction to prove it? None.

From what I can see here:
1. Customer complains
2. Maxis will ask customer to send stopall or send stop to that shortcode.
3. Issue repeated with step 1 and step 2.

What a disappointment!