There is an original address in my mobile phone text message. What is this for? ...

The original address is a transit station, which is the number of the short message service center. If you change it, it seems that you can't receive the text message. If it is not displayed, it may be a multimedia message, but a monthly fee is displayed. If it's not MMS, it's a mobile phone network, and you have to download it to see it. If not, it is the problem of the landlord's mobile phone.