Lidl complaint: Rude at checkout

We went in lidl last Thursday and we went to the checkout with a full trolly and as we usually do my husband put a can of KONG STRONG energy drink on the counter and told the casher we had a full tray she took it of us and we were told we could not buy a full tray I ask if I took them out of the tray could we buy them then.Te answer was a no.(We buy these every week for my son who works for DPD and he leaves home at 4.30 am and arrives home at approx 5pm ang these keep him going ) She had no idea why this had changed and her attitude was not very nice when there was other people waiting.We have been a customer of Lidl since the first shop was opened in Doncaster And I do not mean buying a couple of things here and there I mean a full trolly every week.If this is the way things are going and it rests on the answer I recieve I might just be looking at ALDI .