The incomprehensible mobile phone problem

It's really puzzling to encounter such a situation. I think there are only three possibilities. One is the automatic reply function of some software in the mobile phone. The second one is, will someone use your mobile phone to send text messages to your husband when you are away? Third, it is hanging. There is indeed a way to copy a mobile phone card, which can monitor calls and send and receive text messages ... but it is unlikely that others will do so, right?