Wrong software message seimens a55

This message means that the values read from the configuration memory in the phone don't match the ones that were expected - assuming that the firmware hasn't been modified the most likely cause is a bad connection on the baseband CPU or flash memory.

If you are feeling daring and you have a hot air gun, you could try (carefully!) reheating the chips and see if that fixes it:

The baseband CPU is the big square chip marked "Infineon" and the flash is the one to the right of it - this area normally has a screening can over it, so you need to remove that and also remove the keyboard and display that's attached to the other side of the PCB, since they don't like being heated up.