IPhone not getting some texts?

At least I don't think it is. I'm not sure if it is my phone not receiving texts or the sender's phone not sending texts. A week or two ago, I had someone text me and ask me a question only to find I didn't get the original text from her, but since then I haven't had any problems like this until a few days ago whenever someone asked why I had not texted them back even though I did. Then, the problem seemed to be fixed so I figured it was the sender's phone. But then, the same problem happened yesterday and I told the last message I sent to this sender and he said he replied but I didn't get his response. The problem with it seems to be only from this one person, so I'm not sure if it's my phone or his. If it is my phone, how can I fix this problem? It's very irritating. I reset the phone by holding down the sleep/wake button and the home button, but i'm not sure if that helps at all. Is there a way to fix it without restoring my iPhone?

Delete all your messages same thing happened to me