Being called a liar by The Works!

Hi I made a purchase of three notebooks and a pack of gel pens from The Works on the 14th January. When I received the order I found that instead of the gel pens they had sent three heart slates in error. I contacted them about this they said I had ordered the slates. I checked my order online and found exactly as I had ordered three notebooks and a pack of nine gel pens. I contacted The Works again and told them to look at the confirmation email they sent at the time of ordering this seems to have fallen on deaf ears! I emailed them yesterday and stated that if they dont sort this out I will take the matter further. About three weeks ago they said they would look into the matter. I am prepared to give The Works until the end of this week and then go to Trading Standards. I even asked them to arrange for collection of the slates and to send me the pens I have paid for. If I had ordered the slates my bill would have been £4 more. I feel I am being more than fair. Any advice would be appreciated. Rosie500

Being called a liar by The Works!