Bring the unit back at the store where it was issued if you believe it has some defect before your 7 day replacement expires.
For that battery issue, smartphones consume battery really fast. As you said yourself, the data is turned on and you're using it for calls. Then your music streaming and synch. Those are great factors affecting battery juice. Wala kang makikita na smartphone na tatagal ng 1 day na naka on ang data, ginagamit sa text and calls, may music streaming pa, etc.