Argos have an offer on toys at the moment, if you spend £40 or more you get 15% off. On monday night i reserved some crimbo pressies on line and went into my local store to collect them. As there was a huge queue at the tills i decided to use the card payment machine. I collected my things and went back to the car and checked my receipt to find that the 15% hadn't been taken off and as I'd spent £110 i didn't want to miss out on it. I went back into the store and told the supervisor and she said that because i had used the self service machine instead of a normal till the offer wasnt applied as they had to put it through manually. I said that was fine and asked her to refund what was owed to me back onto my card which she said she couldn't do. When i got home i emailed customer services and explained what had happened and that i would like to be credited the money that i'm owed. I have just had an email back and have been told that the offer had to be done at point of sale there was no way they could resolve the matter.
Does anyone know where i stand with this? There were no signs anywhere to say not to use the self service machine if you wanted the offer. I'm not sure whether to cut my losses and leave it as it is or take it further.

Any ideas?

15% is a bit deal and apart from anything else it's the principle of the thing!

Take everything back - ask them to refund you then repurchase the items.  If you explain why you are doing it I'm sure they won't bat an eyelid

I'd also write a very strong letter to Argos to complain about the lack of advice and lack of clear signage.  You probably wouldn't have minded too much making the effort to pay at a cash desk - but you didn't know you had to

Had ongoing problems with a phone at argos.Bunch of chancers that I would not buy from again.

You probably wouldn't have minded too much making the effort to pay at a cash desk - but you didn't know you had to

this is the point i tried making to them. I wouldn't have minded waiting in the queue if i knew that was the only way i would get the offer but there were no signs saying this. 

There is no way I would let this drop. I would return to the store with all the goods and ask to see the manager. I would state very clearly that I had been tricked into purchasing all the goods through misleading advertising. You only made the purchases because of the offer that was advertised and at no point were you advised that you had to purchase the goods from a certain point to qualify. Say you feel that Argos has cheated you and that you are very disappointed as usually you are happy with their service. Ask the manager to please put things right. If this doesn't work, request a full refund on all the goods. Then go back to the till and order them again with the discount code.
Alternatively, put it all down in an email, again, say that you feel tricked and disappointed etc and send it to one of their customer services email addresses. Their email service is much better than their telephone staff.
Good luck and persevere, you are in the right!

When they said they could not give me the difference I would have taken everything back refunded it and then brought it again - surprised they did nt offer that to you anyhow when you spoke. But would still write to their HO I imagine it is a glitch - but still when you complained I would have thought they would of suggested that to you.