Change SMSC on dual-sim phone I've got a Wileyfox Swift with two SIM cards, running CyanogenMod 13. I can only send SMS from one card/carrier, not from the other.

My guess is that is has to do with the Short Message service center setting.

Changing the SMSC as described on the CyanogenMod wiki only allows me to set one SMSC - but I think I would have to set both.

Is that correct, and how can I set the 2nd SMSC number?

Others have similar problems: ilogik@reddit
Came across this when I had the same issue. A bit late for the OP, but another thing to look out for.

If you go in to:
Settings> Sim Cards> Preferred SIM for SMS messages> Select SIM card> Ask every time