Hello.
First, make sure your iPhone is up to date with the latest iOS what is iOS 12.4.
Make sure that you’re connected to a cellular data or Wi-Fi network. You need SMS messaging to activate your phone number with iMessage and FaceTime. Depending on your carrier, you might be charged for this SMS, because it's an international one. Please, contact your carrier and ask them if you can send an international SMS message and receive SMS messages from short numbers.
Also, check if your time zone is set correctly under Settings > General > Date & Time.