Help unlocked HTC Desire w/ Simple Mobile: Can't receive texts

[Nica]

I have an unlocked T-mobile HTC Desire Z cell phone, with Simple mobile. I have unlimited talk, text, and web. I can make and receive calls, brows the web, and send txts,from my cell phone, but cannot receive texts. So I had to download an app called textfree. However, this app gave me another number so I had to give it to my contacts b/c that's the only way they can text me back and I can read the messages. Is there any way I can set my phone so that I can receive texts from the phone without using this app? It is pretty tedious having two cell phone numbers. Sometimes people call me on the txting number and send me texts on my actual cell phone number. I would love to only use my real cell phone number instead of that other one. Please any suggestions?