Take out the quotes!
cmd.CommandText = "Update BUSON_CALLLOG set UserId='@UserId',RpDateTime='@RpDateTime',CallSubject='@CallSubject', CallDescription='@CallDescription', Priority='@Priority', CallType='@CallType', [Status]='@Status', FeedBack='@FeedBack', FileName='@fileName',FileType='@FileType',FileData='@FileData' where DocEntry='" + CallId.Text + "'"
Should be:
cmd.CommandText = "Update BUSON_CALLLOG set UserId=@UserId,RpDateTime=@RpDateTime,CallSubject=@CallSubject, CallDescription=@CallDescription, Priority=@Priority, CallType=@CallType, [Status]=@Status, FeedBack=@FeedBack, FileName=@fileName,FileType=@FileType,FileData=@FileData where DocEntry='" + CallId.Text + "'"
Otherwise, they aren't parameters, they are text strings!
And parametrize that DocEntry/CallId bit as well - or SQL Injection is still possible on this query!