Gstr 1 for work contract

But when we are entering GSTIN of government in GSTR!, it is showing invalid GSTIN....so may be to file in b2c....

B2C

Dear Sir/Madam 

Our company did the work of constructing a government road, which gave us GST number by PWD department, how would the GSTR 1 file now be?

B2B 

B2C (Others)

Please clear and confirm 

Dear Sri,

Govt Departments Have Regular GST Reg. CAN I UPLOAD B2B 

For Your Reference please find the screen shot of the same

Collect the M-BOOK copy from the government(which contains all the bill details,and  you can fill GST returns-contact for full details-9640054074

Is it necessary for the work contractor to feed the service code in gstr-1