There's no choice but to bring it back to the same casa as they have all the records of your car from the beginning. In line with this ma'am i think you should have all the documents of your complain in hand and if possible ask advice from a lawyer of your rights so that you know what you can and cannot do.

Nandyan na po yan kaya have patience na lang po to continue your claim para baka finally palitan nila buo yun a/c system or mag out source na sila sa nippondenso. Don't bring your car to outside a/c repair shops as they might use that against you to void your warranty claim.