taimatsu no monogatari

I have a mobile phone (PAYG) with Orange. Various things about it bother me, not least that I can get barely any signal in my bedroom in the new house. (I had trouble in the old house, but gettng close to the window helped there. Not so here.) I have had to have bothersome phone conversations in the attic or on the stairs this week, and in order to receive calls I am leaving my phone on a window ledge outside my room (indoors, I hasten to add) and hoping I will hear it ring. This is far from ideal, but I'm not sure what to do about it. Is there anything I can do? Would something like this signal booster actually help?

Of course, I might give up on Orange anyway unless they can do me a really good deal with a better plan, as I am spending way over the odds on the phone now. But how do I know any other provider would have better coverage here?