Prevent UE to read 3G

Dear brothers.
Kindly can anyone tell me what is the parameter in Nokia that let the MEs to go to 2G in CSFB calls directly?
I mean not even read the 3G (cause serving site is 4G/2G)…
Is it from System info parameters or what?
Need to eliminate 3G there because its coming from little far sites.

Set CSFB priority 1 for GSM In REDRT object.