Why do iMessage and FaceTime continue to charge money even after activation? It's been 2 or 3 months that I used to get alert from my carrier that a amount has been deducted and I couldn't find what those charges were for. It's today so happened that the alert of deduction and Apple ID verification came simultaneously and that directed me towards imessage and FaceTime. With a few google searches I found this Apple Support link very helpful, in that forum it written clearly

Depending on your carrier, it can be normal for the activation of iMessage and FaceTime to involve incurring a cost for sending an international SMS message.

And when I searched for the cost of international SMS in my country and carrier, it was same as the deduction amount that I got alerted for. Here is a screen shot of a SMS that I get

And soon after this I get a deducted alert from my carrier. To ensure that my FaceTime and iMessage are toggled on and activated let me attach images of them:


So, now it's clear that my Iphone 7 is sending international SMSs for the activation of imessage and FaceTime (which I say is already activated). Now, I have two questions:

Why it is sending those international SMS even after activation is done?
How to stop it? It has already cost a good deal of deduction.
The most logical answer to this is that it is not sending international SMS messages after activation is done, so it must be something else your carrier is charging you for.
I would contact your carrier to get an explanation of the costs.
As far as I understand, many carriers have business relationsships with Apple and ensure that you are not charged for FaceTime/iMessage activation. You can check a list of carriers here:
https://support.apple.com/en-us/HT204039
UPDATE
You have updated the question with the requested information.
The phone number you quote is indeed an Apple registration number in the UK. Your own phone number seem to be in India. The carriers I know in Europe usually do not charge their customers for Apple registrations, but your Indian carrier apparently does.
The text message you have is not the FaceTime registration message - it doesn't look like that. It does however look like a standard receipt that indicates that a has been delivered succesfully.
I would try disabling and enabling FaceTime/Messages (i.e. specifically your phone number from FaceTime/Messages) to try to trigger a re-registration.
If that doesn't work, contact Apple to work out why it keeps trying to register.