Spoofing?

Hello, I have noticed that on my phone bill - Messaging details - there are numbers listed with txt sent and received but I never see these numbers on my actual iphone or receive these messages to my ACTUAL phone. FOr example it showed 10 messages sent / 13 messages received from the same phone number at 4 am, when the phone was NOT being used and there were no actual messages on my phone.  The agent I talked to said my phone isn't compromised, and when I asked about spoofing she said those numbers don't show up on my phone bill.  Anyone have any suggestion on what to do here?