SAA Booking service separates families from kids

My daughter in law and two very young kids from the US booked return to Cape Town from NY together. The seats she reserved accommodate a basinet for a baby and there are only a few of these on the plane. My wife in Cape Town booked separately on the same return flight specifically so she could help them on the CT NY leg. She obviously needs to sit with them for this to work. When we called a couple of days ago, SAA said the seats alongside the kids were "restricted" and could not be booked till 24 hours in advance, no matter what the special need. We could not find out what "restricted" meant. We now called 72 hours in advance to see what we could do, and were told the seats next door had already been "bought" by someone else! No amount of querying how this could happen if they were "restricted" and what we needed to have done, resulted in any sensible answers. Just no reasons and no solutions. My wife is now sitting 5 rows away. How is she able to help from there? It's no wonder SAA is in trouble, and constantly being bailed out, they have no clue about service in a global market. SAA's service is appalling and this is not the only example. Next time the family will all fly United to NY, in more ways than one!