This is an issue that crops up with some Samsung phones - and not just on 48. If you search the community forum then you will find many previous posts about this. And if you Google you'll find lots more about the same issue on different networks and in different countries. Unfortunately I've never seen a clear solution to this problem. If you need to contact 48 support about it then see the link in my signature below or email them at email@example.com
However I doubt that they're going to be able to help otherwise there would be a FAQ on this issue and how to fix it.