Payment for SMS to number 447537410217

That's because iMessage and FaceTime use background SMS message to activate and connect. That is Apple's authentication server in the UK.

Either turn off and sign out of iMessage and FaceTime or switch to a supported iPhone carrier.

Supported carriers do not charge for those messages.

They took the payment because you are not using a carrier that partners with Apple. You will continue to see these charges on a regular basis if you want to use FaceTime or iMessage. Either switch to a supported carrier, or disable iMessage and FaceTime. Note that you must disable them, just turning them off is not sufficient. Here’s how:

FaceTime: Go to Settings/FaceTime, turn it on if it is off, tap on your Apple ID and tap Sign Out

iMessage: Go to Settings/Messages, turn it on if it is off, tap on Send & Receive, then your Apple ID, and tap Sign Out

Two more international texts will be sent after you do this, but they should then stop.

If you you dual SIM and change you number for iMessage from eSim to normal SIM then your carrier may charge you for this. Refer Apple article. --> Using Dual SIM with an eSIM - Apple Support

An extract from the article above is given here

"

Send messages with iMessage and SMS/MMS

You can use iMessage or SMS/MMS to send messages with either phone number.* You can switch phone numbers before you send an iMessage or SMS/MMS message. Here's how:

1. Open Messages.
2. Tap the New button, in the upper right corner of the screen.
3. Enter your contact's name.
4. Tap the current phone number.
5. Tap the number you want to use.

* Additional fees may apply. Check with your carrier.

"