In Home quality check?

Someone came to our house and said that they detected a weak WiFi signal and offered to replace the lines to get a stronger signal. One of us was working at home online so we couldn’t have an interruption in service. They said they could come back at a later time but these home visits only occur at the end of their work day (ie if they finished their work early, they can come over and check). Is this an xFi service? I vaguely remember this being mentioned by an xFi customer service rep when we replaced our modem. I’m hesitant at letting someone into our home.