If you've owned your 12-inch Retina MacBook for less than a week, since new, ask
the reseller if you can trade it up or across for a MacBook Air. This is easiest if you
bought direct from a retail Apple Store; not independent authorized reseller. In US
& few other regions, you have 14 days from the day of purchase to contact Apple
and arrange to return the computer. Elsewhere, the option may vary, or not exist.
And if you did not buy direct from Apple (retail store or official site store) you may
ask the unit be inspected and repaired under warranty. The basic initial coverage
should suffice; for 90-day support and one year service. The extended AppleCare
adds cost but may serve to secure the investment; or incentivize a second buyer
to consider your used MacBook if it still has an active AppleCare plan intact.
For the inconvenience of USB-C ports and no separate power port, the MB/Air may
be a better concept. My preference remains with the older design 13-inch MacBook
Pro with optical drive, & the ability of a user to upgrade the RAM chips; still available
in the online Apple Store and occasionally also in their 'refurbished' section for less.
Hopefully you can resolve this issue in one of the ways that should be available to you.
Good luck & happy computing! 🙂