Was your iPhone reasonably near when you were speaking to your husband?
My best guess would be that you said something to him which Siri (the voice-controlled personal assistant on your iPhone) picked up as “call [whatever your friends’s name is]”. It called her, she didn’t answer and whatever you were saying to DH went to her voice mail.
If you said say, I’ve just called the doctor, Siri might pick it up as "call Dot."
If you only have only one person with whatever name Siri thought it heard in your contacts and only one number for that person it would make the call. If you have more than one person in your contacts it could chose from and/or more than one number for one person it would ask more questions to determine which number to call.
You can switch off Siri in your iPhone settings.