Buy a throwaway commlink, a sleaze dongle and a temporary commcode. Connect the sleaze dongle, form your avatar on the throwaway commlink, switch to the temporary commcode and make the call. Reboot your persona after you made the call and then change back to your regular avatar on your regular commlink. Switch back to your regular commcode. Save the sleaze dongle, throw away the throwaway commlink and don't use the temporary commcode ever again.
("Temporary commcodes" or "switching commcode" is not RAW).