SPAR does not accept swops or returns bought at another SPAR store.

I wanted to swop an item that I bought at 1 spar store at another as I'm aware that all are part of 1 group or franchises thus honor a customer from another. I believe that this is unacceptable from a group of stores that operate under the same name. SPAR S.A. confirmed that one cannot return or swop at another store and that they are not a franchise business - then what are they?