Denied Return Refund

I ordered an extra length king-size mattress for my bed. Upon delivery on Friday, 15 April I discovered that the extra length was too big for my bed and a normal king-size would be sufficient. I Immediately called dial a bed to inform them of my issue. This was also suggested by the delivery company who said that they do this all the time (delivering product that is incorrect and then having to return it). Upon speaking to the sales person I dealt with they informed me that they would do a difference refund on Monday, 18 April. <br> On Monday the manager of dial-a- bed has called to tell me that they will not be doing a refund difference for me because they cannot tell whether the bed has been used or not. On top of that the manager has said that I will be liable for delivery costs once again for a new bed and that's the difference that would have been the refund will now be kept by the store. <br> <br> I can except having the difference refund deducted for redelivery costs however I cannot except that the refund will not even be looked at after I had spoken to staff who informed me that this is very possible to return the bed and get a difference refund on Monday.