An OAP was fuming after being charged more than £1,200 for a packet of biscuits when she did her online shop during the coronavirus pandemic.
Susan Hunter, 74, ordered groceries worth £79.54 online from Sainsbury's, to her home in Clarkston.
But she was stunned when the bill was processed, totaling £1,288.19.
It meant one packet of biscuits was charged at £1,212.40.
Mrs Hunter, who is shielding along with her husband Robert, 76, who is recovering from cancer, was appalled by the error - and said it could have left a person unable to pay rent or bills, or even brought on a heart attack.
The couple used to run a shop and said it should not have taken a month to get refunded.
Mrs Hunter said:"Maybe if someone didn't have the money there it was taken out, it would have left them unable to pay their council tax or left them strapped without food or unable to pay rent or mortgage.
"I hope this doesn't happen again.
"I wouldn't like it to happen to anyone else.
"It could give somebody a heart attack or a stroke or something.
"Times are quite difficult enough as they are."
She spent every morning for a week trying to get the fee reversed - which happened nearly a month later.
Mrs Hunter added: "It was just so stressful, and even more so because we couldn't get speaking to people to resolve the problem.
"Although they have a customer care line, getting through to it is not easy.
"I actually even tried phoning the head office in London, then it said this number doesn't take calls.
"I know they must be up to their eyes in it at the moment, but they're also making an absolute fortune.
"Problems like this should have a solid system in place to reverse them.
"I used to have a shop and if you'd have done something like that, you'd obviously see it right away.
Mr Hunter added: "Had that been an OAP or even an elderly widow on her own, or somebody on a basic state pension, it would have cleared them out.
"Susan was certainly on the phone a lot trying to sort it out.
"It should be a simple process of resolving a mistake on their behalf."
A spokesman for Sainsbury's said: "We apologise to Ms Hunter for her experience and for any inconvenience caused.
"This appears to be an isolated mistake and we are looking into how it happened."
