Group text has some how change one members number to her home number

We had a group conversation going. We did not text for over a month then somebody texted the group and somehow two of the numbers got changed to the persons landline, i.e. their home phone number instead of their mobile number. I have been spending hours trying to get this changed. I have tried to start a new group conversation. No matter what I do Siri or something remembers those numbers every time. I put in those six peoples names those same numbers come up and those two members never get the texts.