SMS messages not complete

I am not able to see all SMS messages on my children's phones.  I have 2 phones on my account and they both do the same thing.  I can tell messages are missing from the conversation it will say there are 75 messages and then only show like 10.  I am also not able to see images, I have looked at the actual message and there are images but then it doesn't show them in my account.  It has done this since I have had the account open, they both just got new phones in Sept and it still does it on both phones.  Is there something wrong with my account?  For what I paid I should be able to see all of my kids texts and images, otherwise it kind of defeats the purpose of having the account.