Yo think Sainsbury's do this on purpose.

[FATFATFATTY]

Do not fully refund all items returned from substitutions on online shop.
Then IF you notice give a voucher which, if you amend your shopping, is then removed.
I am so mad, only recently realised need to check refunds were accurate, hadn't realised how often thet aren't.
Have just realised today that the vouchers were removed every time I amended a shop.
I have deleted lots and some are expired.
Damn! Damn! Damn!
I am sure it is a profit making scheme.
I am financially incompetent and not good at checking up as have very bad baby brain.

They also relentlessly overcharge me for items that are on offer.

And on the self-service and machines (incl scan and go) they don't automatically take off any special offers e.g. 3 for 2 etc. You have to go through to the pay screen and select back in order to re-adjust your bill. Last time my bill went from £58 to £46. Wonder how much they make through people not realising this.

And here's me thinking that Sainburys was a charity not a profit making monstrosity.

that happened to me Firky! I bought 3 bags of sweets, 3 for £3 (not the normal £2 each) and they came to £6 and the bill was £4 more than I thought. I hit the help button, then pressed finish and pay and there it was, £4 less! Sains!