There was some development attempt to try to add support for `long/long long` data types, I will look over it when I get some time.
But the `kamcmd` is somehow stalled, with no active developer taking care of it. You should use `kamctl rpc ...` or even better the `kamcli`:
- https://github.com/kamailio/kamcli
If nobody commits to maintain `kamcmd`, it may be removed in the future, so it is recommended to move the workflow to a maintained ctl tool.