Fret popping up?

I've had this lanikai lu21T for about 3 months and i noticed that my C string had a very tin-like twang sound to it. So i took it to my local music store and they said that a fret was popping up so they hit one of the frets down with a hammer and oiled the bridge. Now 1 day later the G string first fret has that same annoying twang sound. I'm going to try to hit frets down but is their a better solution?

Yeah, sure. If it's in warranty go to the store from whom you bought it. They might fix or replace - although the attempted fix by your man could muddy the water to some extent.

If that doesn't work out then one fret should be a fairly simple job for any decent guitar tech or luthier to fix.

Don't panic. Should be quite easily sorted, but may cost a few quid/bucks.

I took it back to the music store and he attempted to tap down the fret one more time. It just wont stay down. I'm supposed to see the owner of the store and he is going to make the bottom fret jagged supposedly. *fingers crossed*