Hi, you can apple for a Credit Limit Increase and see if Goldman Sachs will increase your available credit. Here is a support article that covers how to use your iPhone or iPad to apple for a CLI,
https://support.apple.com/en-us/HT212307
I believe you can also pay a portion of the total cost, apply an Apple Gift Card and/or trade in an eligible product. Any of those will reduce the cost of the item you want to purchase. Here are several support articles that go over the Installment Plans and also how to pay the installments,
https://support.apple.com/en-us/HT211204
https://support.apple.com/HT210644
I hope this helps.