Indirectly accused of *****ing

I went to woolworths after shopping for some baby items (milk nappies ect ) from another store , The security saw me coming in with the items and it was not a problem , after I shopped for what I needed I was approached by security asking me \Did you pay for that milk in the baby's pram) .... I asked her since when do we have to check in what we come in with into the shop