Phone Not Texting Proper.

Just got a new Straight Talk Motorola EX124g & ported my previous Straight Talk phone number to it. I could text out but wasn't getting responses. I later turned on the previous phone to get some phone number info & learned that there were several unanswered text messages which i thought odd because i thought that phone was disabled. Those messages were the responses to the text messages sent from the new phone. So, I can send & recieve text on a disabled phone (or so I thought) and I can send but not recieve text on my new phone.   Don't want to carry 2 phones around anymore. Can U Help?