Default [Q] (Lenovo A516) No service when change 3G network mode.

Hi everyone, hope you can help me.
Ive accidently formatted my lenovo a516 Allegro ROM without backup actual nvram. Then i got nvram err warning and 3G no service. Ive already solved nvram warning and fixed my imei. After that 2g network mode is fine but when i change to 3g still no service. Any ideas how to fix 3g issues?
Btw i think my lenovo is a516_ROW.. Not CN.