Even the fake reviews from not a verified purchase were removed, the rating will not be changed?

We faced the competitors' attack that we got many negative reviews from Not a verified purchase in Jan. and Feb. And the rating of my product was dropped from 4.3 to 4.0. After reporting, thanks to Amazom's help that about more than 10 negative reviews were removed. Although the negative reviews were removed, the bad rating did not change and still stayed at 4.0. After checking with seller support. They answered me that the rating will not be changed because it is based on Amazon automatic algorithm. Is it correct understanding? If it is, It is so frustrating. We cannot believe It is so easy for competitors to attack other sellers’ business.

We believe this kind attack will keep going and do not know what we can do now.