This solution is described in section HLR query while message routing.
To simplify let's assume, that this service will be provided to users free of charge.
1. Configure [HLR routing|Routing of HLR queries]].
This is described in section Configuring routing of HLR queries.
2. Choose configured Route class on user group or user of interest.
3. Set Inbound -> billing pack for HLR = 'zero' on user group or user of interest.
4. Configure Message routing as described in section Configuring messaging solutions