I have a Droid 2 with Verizon. I have a friend who is also on Verizon who cannot receive my texts. Help?

I know for a fact the person did not block me. I went to Verizon and the only thing they told me was that it seems to be a problem with the other person's phone. I can receive text messages from the person but they cannot receive any from me. My calls also won't make it through. I had Handcent SMS installed on my phone, but I deleted it in fear that it could be the cause of the problem. Still no luck though. The other person has one of those water proof flip phones, if that helps. Has anyone else had this problem or know how I could fix it?