Iphone 5s switching between edge and 3g

Hello, I have switched from a 4s to a 5s today and I am having problems with the mobile internet connection. On my 4s I always had a 3g connection when I am at home. On my 5s it keeps switching from 3g to edge then back to 3g after a while. If i put it on airoplane mode when it is on edge then take it back off airoplane mode I will have a 3g connectiong again for a while. Is this a hardware or a software fault?