Can u use myhabit credit on amazon?
not directly, but if you wanna go through the bother of ordering something using your credit and then returning it you should get the refund as an amazon credit, as per the t&c's:
If you originally paid for the purchase with gift card credit, or with a combination of gift card credit and payment by credit card or debit card, you will receive the refund in the form of Amazon.com gift card credit only.
I wonder what they would say if you called up and said that this is your intention and if they want to save their money on shipping then they should just convert it to amazon credit.