If you mean Mikomi, rather than Makomi, then you have an Argos Own Brand product and so (as it is under year old) you need to take it back to them for a refund.
Don't worry about the receipt if you have lost it. First of all it IS an Argos product and so you MUST have bought it from them. Second, when you bought it, you filled in a form in the store (as required by law) and so the shop will have proof of the date your purchase.
t, October 2008