Life threatening situation: nobody can call me!!!!

Since Christmas, I have a horrible problem as I cannot make or receive calls at home (everywhere else it works). When I fail a number, it does not even ring or give me any kind of message (same for people who try to call me). I have full signal (4 bars on my iPhone), and the problem obviously is related to a SIM card problem. The local store did a SIM swap, and it worked only for a day. My mobile phone is my one and only contact number.... I am awaiting a transplant, so the hospital cannot even reach me when a donor would come up. For me, its is a life threatening situation, and nobody wants or can help me.