In the US, if you bought DIRECTLY from Apple, and took delivery less than 14 calendar days ago, you can return your Apple equipment for a refund.
This effectively means you can renegotiate to use a Credit plan, IF you can qualify for one. (You may or may not have to swap computers.)
The plan available uses Apple's credit-card concession (in the US it is Barclay's Bank). You must apply for their payment plan. I have no idea whether you can qualify. I have no idea whether any similar payment plan is offered in your county.
In the US, the plan is managed through a credit card issued in your name. If you have the discipline (and the money) to make AT LEAST the required payment (typically 1/24th of the total every month for 24 months without fail) and are not late or short AT ALL, you are not charged Interest.
However, if you are EVER late, or EVER Short, Interest at 25 percent is charged on the entire amount for the entire two year period, and continues until payed off completely. Also, since it is a Credit Card, you may be tempted to use it for other purchases, which must be payed off immediately or the entire amount will be subject to Interest for the entire two year period at that very high rate.