Samsung Ac - Foul smell from Samsung AC

I have bought two * stars *.*-ton AC from Samsung in March ****. They were the best available ACs in the market. Each AC cost ***** rupees and I bought two of them costing around ***** rupees. To my surprise, within * months into using the AC, there was foul smell emitting from both the ACs. I have lodged multiple complaints with Samsung customer care. Executives from the local service centre in the name of Samsung would visit my home and in the name of service would pour hot water, lemon water, Dettol water and so on. After each service, they would say the issue would be resolved but it didn't. Ultimately I approached Samsung through their 'Write to our CEO' section on their website and through them got the inner coil components of both the AC replaced. I used the AC rarely after the summer season and now in the current summer season when I started to use the ACs after few days both of my AC started emitting foul smell again. I have now raised the request again and they are saying they will replace the inner coil again. But the service from the local service centre is pathetic.