IPhone 3GS says 'no service' inside, anyone know why?

[JessKonstantine]

I bought my friend a iPhone 3GS off eBay and it said it's on O2, so I tried a new O2 sim in it and it just said no service, so we tried a orange one in it and it only has service when I'm outside but none at all when we go inside, does anyone know why, is that just what it's like or is there something I can do so it has signal? Thanks for any help.

 

[Micdaz8]

I have had trouble getting service inside buildings before too. I've found that most of the time it has to do with the thickness of the walls and what they're made of. Concrete tends to limit wireless waves more than wood or drywall. And the thicker the wall the fewer the waves can get through.