There is no range option in aria2c.
But if your ISP looks Contet-Length header to block large file transfer, you may trick ISP using --enable-http-pipelining option.
It requests usually 1MB block of file in one request, so it does not appear as a big file. It is not as efficient as bulk transfer, but I think it works if server supports pipelining. Of course, it does not work FTP server.