I bought my Nintendo Switch on 22 July 2017 , and right now the "Low Battery" message for the left joy-con appeared , the right joy-con haves the 75% of the battery , the left joy-con has the 15% battery. The question is : ¿Should I call to Nintendo to report the problem? ¿They will change my joy-con?

Have you tried like, charging them?

I think he's trying to say the battery is pretty weak.

Well, I think you should report your problem

report it to Nintendo, they'll probably send you a new one, just means you won't be able to play switch unless you have another L Joy-Con until the new one arrives