I can't receive or send texts on my iphone?

I have just recently upgraded to an Iphone 5s from an HTC Wildfire and for some reason I can't receive or send texts when I'm in my room. My room is very bad for Wi-Fi connection but I don't see why that should affect my ability to send and receive texts. On my old phone I had no problems at all with text messaging whilst in my room, can some help me with this?

Added (1). Also I'm still on the same phone network

Check the message center number first in the settings of the phone, usually the cause