iPhone: Sending international SMS
If your iPhone is used with a carrier not found in the wireless carrier articles, an international SMS is sent each time you activate iMessage/FaceTime. (One SMS Only)
If there are 4 SMSs that indicates you have activated iMessage 4 times.
Each time you change the SIM or activate iMessage/iCloud/FaceTime you must have got these warnings (As Shown in the pic below). If you had tapped on OK then only then the SMS is sent .....
See the pic below
Do not activate iMessage for phone number, as shown in the pic below.