iPhone 15 keeps going into sos mode

so I just bought my first iPhone and it’s the 15 my service is through straight talk so I called and got phone activated and everything was working fine for about an hour then all of sudden it went into sos mode only temporary fix I have found is to keep activating a new eSIM it’ll work fine for a couple hours and then go back to SOS mode then I’ll just activate a new eSIM does anyone have a permanent solution for this problem or knows why this is happening to me