How long have you had them, as since your birthday doesn't really help.
The usually come with a basic 12mth warranty, take them to wear you bought them from if within 12mths, explain the issue, see if they'll replace them.
If not then suggest you ring Samsung or visit a Samsung Store, as it may be a faulty battery.
When you get your replacement, do not leave them charging overnight, that bloats the battery by overcharging.
