SIM card loses connection

Samsung galaxy note II. I had a problem with the charge port and replaced it. Now the unit charges but it will work for a couple minutes but then will all of a sudden lose the SIM card and drop connection. It also is having trouble seeing the battery voltage, it will go from 98% to cutting off from low voltage. When I plug it back in it shows the 98% charge level. This does happen to be the Verizon version unlocked/new os.