Do you have a registered complaint number with Carrier people? If not, then get your complaint registered with them officially as soon as possible. Else think that you are waiting for a coming train without any ticket in hand.
First follow up with their customer care, using that complaint Number.
Be sure to keep a log of voice calls as and when you reached out to them. You may record the calls (secretly) for your record keeping but they are not admissible legally as proof.
Make sure to email them and keep a record of all conversation with them.
Be persistent.
The basic idea is Carrier will not want to lose its customer and they want to keep their customers happy. So, they will find a solution for you either by offering a new unit at some discounted price or by getting it repaired at the earliest.
You need to get in touch with the "service area manager" catering your area. Get his number from the service centre people . They should give it to you.
You need to get in touch with the right person and then it should not be that tough.
Thanks,