try reply STOP to that number? And contact Celcom customer service, ask them to check and cancel it for you.
I have the same problem after buying a new chinese phone here in Cambodia. There is a virus built into the actual Android UI operating system. It is a ZOPO Color X5.5
The subscribe message for me, says to send OFF to 6366 .. which I do .. but then as soon as WIFI is off, it does it again.
I tried everything including installing anti-virus software, even doing a hard reset .. still the same issue.
The anti-virus software did find the virus (360 security) but as it is the main operating system part of the Android device, it cannot be disabled or stopped.
Only solution for me anyway is to buy a new phone.
The reason why anti-viruses won't work is because there no viruses on your phone, rather the website's advertisements.
So there has been a huge surge of reditect ads that take you to shady sites that, from your browser, make SMS subscriptions and cost you money. This honestly isn't the fault of us Celcom or the content provider, but rather the middlemen: ad networks.
To prevent this, all you need to do is 1) don't use mobile data, 2) use an adblock browser.
My advice is when you see any pop-up that says "please press Allow to continue", never do it and push the Back button to leave the site. Or if it keeps redirecting to the same pop-up, close the tab immediately. This has been a very serious and deep-rooted issue that even Google themselves have a hard time dealing with it,