a) usually, when you set up 2fa you get a set of 'recovery codes' for this exact situation - do you not have those? b) usually, there's an option to authenticate via SMS or reset your 2FA via email - does Amazon not offer any alternative? Ultimately, though, you need to exercise care when setting up 2fa - make sure the device you use is one that you're going to have around for a while, or you have a decent way of migrating to a newer device if necessary.