Q: Low volume issues on iPhone 6sPlus

I recently just got an iPhone 6s Plus (16GB) and everything was working fine until it suddenly got volume issues while I was playing music on full volume on speaker. I tried resetting everything and also not restoring from iCloud but I never got the full volume back, it still plays on speaker but very low even when it is already in full volume. App sounds are also affected, sometimes they don't play at all and I have to restart every now and then to get them back. I've been using it only for a day when this happened, now I don't have full volume when I play music on speaker or any videos in app and it hasn't even been a week since I got this.

Is anybody else having low volume issues on their iPhone 6s Plus? Is there anything else I can do on my own before taking it to an Apple Store? I'm really disappointed.

Thanks guys.