Mister, did you know that
Siemens C66 - GSM 850/1800/1900=Siemens CV65 for Vodafone=Siemens CT65 for T-Mobile=Siemens C65 ??So you can flash it with C65 Fullflash.
You can not use SST, you must use V-Klay or x65-flasher.
First, do not flash it, try to repair it with PapuaUtils and testpoint.