I wonder whether my mac book pro 15 inches battery is free to change in this time.

The recent news of a battery replacement program concerns certain 13-inch MacBook Pros (non Touch Bar), manufactured between October 2016 and October 2017.

13-inch MacBook Pro (non Touch Bar) Battery Replacement Program - Apple Support

So none of the 15" models qualify.

While batteries of certain models will be exchanged under the replacement scheme, that does not exclude the overall guarantee that your battery should be fit for purpose. When and where was your machine purchased? What country are you resident in.