Signal problem in any mobile can be solved different ways, some time signal problem solved by updating software or some time by changing signal IC. In nokia 101 signal shows full bar but when we try to make call it shows error call failed. Also phone did not receive any call and messages. I have solved many same cases by working on Main IC (cpu). Just rehot cpu to solve this issue, still problem not solved then reball cpu carefully.
Nokia 101 signal full but can not receive calls and messages problem solution trick, Work on main cpu ic.