I did this "Dial *3001#12345#* " and it show on my phone Errror performaing request unknow error.APN field show: sp.mb.com.No idea what or where "IPv4" is.
My iOS 12.1.3.I followed your the instruction, but it still not working.I don't know if that a good idea to switch it to PM. I didn't know that it's so complicated.