Hi
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.
The message is sent in the background by your iPhone (to Apple's servers in the UK) when setting up these services. Some carriers do not charge for this SMS message, whilst others do.
If you are experiencing issues with activating either or both of the services, then follow the steps here:
If you get an error when trying to activate iMessage or FaceTime - Apple Support
If you are unhappy with being charged for such messages, then you may wish to contact your carrier / cellular service provider and let them know.