Default [Q] I Keep Getting MMI Error

Hi there am not to tech say but I know a little. Any how I keep getting a Invalid MMI Error code and connection problem code. What does this mean and how do I fix this. I can't call my voice mail by holding down the speed dial number 1. All my contacts have a 1 then area in front of it. I also am having trouble using my WiFi hotspot it says mobile number not found. I originally bought my phone from Verizon and decided
to switch to t-mobile so I had my phone unlocked. Could this be the problem. T.I.A.