Trolley boundaries

On the 25 of July I went to Boxer Somerset crossing did my groceries and went to KFC while I was waiting for my oder someone working for Boxer came in and ask shouting " who owns this trolley" I rep**** it's me he then asked me to come he wants the trolley back I told him I won't do that I then went inside boxer asked for the manager because I wanted to know if their trollies are not allowed to leave the shop she said "yes" I just want to know from boxer do we buy their food and take our groceries by our heads walking around Somerset crossing center? I never saw anything written that we not allowed to take trollies to other shops until I was rudely shouted.