The cellular data won't affect your ability to make calls and send basic text messages. Try dialing *228, option 1 to reprogram the phone to the Verizon Wireless network.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
I have this same problem. My phone just says searching on top. I have no signal so i cant call or send text or connect to 3G. I also have a Iphone 4. I cant even dial the *228.