Hi, received my SoundCore boost on Wednesday and managed to test it out on a few calls (normal and whatsapp). Unfortunately it's pretty much useless for this functionality due to the built in mic. People just can't hear you properly and switching back to my phone mic solved the issue. I was only sat a foot away from the speaker
I'm not sure if I received a unit with a faulty mic but I won't really use it for calls that much so it's not worth me returning it.
As a bluetooth speaker for music though it's amazing. Great sound.