Coop Diet Coke £11.00 NOT £8.00!!!

for several weeks you are listing 24 cans of diet coke in Coop as on offer for £8.00 ... I visited Coop again today (08 March) and it is still £11.00 for 24 cans as it was weeks ago! So why are you still listing it as £8.00??? A great app ... BUT?!!!